Windows: official port -- UCRT static build, UTF-8 throughout, Low IL sandbox, ncurses TUI, installer; v0.6.0

Build
  * cross build switches to pkgsCross.ucrt64 (shell-win.nix); curl (Schannel),
    winpthreads and ncurses 6.6 are linked statically, so the release is
    cst-agent.exe + busybox.exe (busybox-w32 Unicode) with no extra DLLs
  * windres embeds a manifest with activeCodePage=UTF-8 and a version resource
  * ncurses 6.6 Windows console driver patches (mouse button state, A_DIM,
    wide-char declarations): scripts/patches/
  * scripts/bootstrap_msys2.sh builds the same release natively in MSYS2
    UCRT64; PR #1's MINGW64 notes now point there
  * vendor/tre-regex (musl's TRE) provides <regex.h> on MinGW

UTF-8
  * paths cross the system call boundary as UTF-16 (*W APIs); console code
    pages set to 65001 and restored on exit; files are read and written in
    binary mode
  * child output that is not valid UTF-8 is decoded from the console, OEM or
    ANSI system code page
  * read_file hides CR; edit_file, apply_patch and write_file keep CRLF line
    endings and a UTF-8 BOM

OS layer and processes
  * os_dir_* and cst_fnmatch replace the POSIX-only directory walks in
    subagent, plugins, skills, undo and fs_tools; realpath / path_under and
    symlink rejection work on Windows
  * every child goes through CreateProcessW with its own environment block
    inside a Job Object, so timeouts and Esc end the whole process tree

Sandbox (auto mode, "auto · lowil")
  * run_shell runs with a restricted Low integrity token; the workspace gets
    an inheritable Low label once, the sandbox TEMP is labeled Low, and the
    credentials file gets a no-read-up label
  * drive roots, the profile and system folders are never labeled
  * network commands still ask, since Low IL does not block the network;
    Access denied and MSYS2's 0xc0000142 offer a rerun outside the sandbox
  * /sandbox lists labeled folders, /sandbox reset-labels restores them

TUI
  * raster console fonts are switched to Consolas / NSimSun while running
  * the home logo falls back to text when the console font lacks U+2580
  * mouse drag copy goes to the Windows clipboard

Distribution
  * scripts/install_windows.ps1 installs a Gitea release into
    %LOCALAPPDATA%\Programs\cst-agent and adds it to the user PATH;
    cst-agent-update.cmd reruns it; scripts/release_windows.sh uploads the
    zip with the token taken from the environment
  * scripts/run_windows.bat is gone; docs/README-windows.md is rewritten

Tests
  * new test_lowil, test_win_utf8 and test_os_dir; tests made portable
    (cst_test_util.h)
  * scripts/win_test.sh and scripts/winvm/ run the suite on English and
    Chinese Windows Server VMs as Administrator, a standard user and a
    Chinese user name: 29/29 on all six

src/tui.c

@@ -41,11 +41,12 @@
 
 static int g_nocolor; /* NO_COLOR */
 static int g_ascii;   /* non-UTF-8 locale or CST_ASCII=1 */
+static int g_logo_text; /* console font lacks the logo's block glyphs */
 static int g_utf8 = 1; /* locale can show non-ASCII text */
 #define HAS_COLOR() (!g_nocolor && has_colors())
 
-/* Curses: ncursesw on Unix, PDCurses (wide) on Windows. */
-#if defined(CST_USE_PDCURSES) || defined(_WIN32)
+/* Curses: ncursesw (Unix and Windows), or PDCurses (wide) on Windows. */
+#if defined(CST_USE_PDCURSES)
 #ifndef PDC_WIDE
 #define PDC_WIDE 1
 #endif
@@ -62,10 +63,23 @@ static int g_utf8 = 1; /* locale can show non-ASCII text */
 #ifndef KEY_RESIZE
 #define KEY_RESIZE 0632
 #endif
-#define wcwidth cst_wcwidth /* MinGW often lacks wcwidth */
 #else
 #include <ncurses.h>
 #endif
+#ifdef _WIN32
+#define wcwidth cst_wcwidth /* MinGW often lacks wcwidth */
+#endif
+
+/* The Windows console (conhost/ConPTY) loses wide characters on insert or
+ * delete-character, so curses must repaint cells instead. */
+static WINDOW *tui_newwin(int rows, int cols, int y, int x) {
+  WINDOW *w = newwin(rows, cols, y, x);
+#ifdef _WIN32
+  if (w)
+    idcok(w, FALSE);
+#endif
+  return w;
+}
 
 #ifdef _WIN32
 static void cst_usleep(unsigned usec) {
@@ -1876,10 +1890,10 @@ static void git_branch(const char *dir, char *out, size_t sz) {
   FILE *f = NULL;
   for (int depth = 0; depth < 64 && d[0]; depth++) {
     snprintf(p, sizeof(p), "%s/.git/HEAD", d);
-    if ((f = fopen(p, "r")) != NULL)
+    if ((f = fopen(p, "rb")) != NULL)
       break;
     snprintf(p, sizeof(p), "%s/.git", d);
-    FILE *g = fopen(p, "r");
+    FILE *g = fopen(p, "rb");
     if (g) {
       int ok = fgets(line, sizeof(line), g) && strncmp(line, "gitdir: ", 8) == 0;
       fclose(g);
@@ -1889,7 +1903,7 @@ static void git_branch(const char *dir, char *out, size_t sz) {
                     ? snprintf(p, sizeof(p), "%s/HEAD", line + 8)
                     : snprintf(p, sizeof(p), "%s/%s/HEAD", d, line + 8);
         if (n > 0 && (size_t)n < sizeof(p))
-          f = fopen(p, "r");
+          f = fopen(p, "rb");
         break;
       }
     }
@@ -2322,7 +2336,7 @@ static void draw_home(tui_t *t) {
   getmaxyx(t->logw, h, w);
   int box_top = t->in_y - t->log_y;
   int box_bot = box_top + t->in_h;
-  if (g_ascii || !g_utf8) {
+  if (g_ascii || !g_utf8 || g_logo_text) {
     int x = (w - 8) / 2, y = box_top - 2;
     if (y >= 0) {
       draw_ansi_at(t->logw, y, x, 3, "cst", CP_LOGO_DIM, 1, 0);
@@ -2805,12 +2819,107 @@ static int input_visual_rows(const tui_t *t) {
   return rows;
 }
 
+#ifdef _WIN32
+static DWORD g_con_in_mode;
+static int g_con_in_saved;
+
+/* QuickEdit makes the console select text itself and swallow the clicks;
+ * it is off while the TUI owns the mouse and restored on exit. */
+static void win_console_mouse(int on) {
+  HANDLE h = GetStdHandle(STD_INPUT_HANDLE);
+  DWORD m;
+  if (!GetConsoleMode(h, &m))
+    return;
+  if (!g_con_in_saved) {
+    g_con_in_mode = m;
+    g_con_in_saved = 1;
+  }
+  if (on)
+    m = (m & ~(DWORD)ENABLE_QUICK_EDIT_MODE) | ENABLE_MOUSE_INPUT |
+        ENABLE_EXTENDED_FLAGS;
+  else
+    m = g_con_in_mode | ENABLE_EXTENDED_FLAGS;
+  SetConsoleMode(h, m);
+}
+
+static CONSOLE_FONT_INFOEX g_con_font;
+static int g_con_font_saved;
+
+/* conhost has no glyph fallback: NSimSun, the default on Chinese systems,
+ * draws U+2580 as an empty box. */
+static int win_font_has(const WCHAR *face, WCHAR ch) {
+  HDC dc = CreateCompatibleDC(NULL);
+  if (!dc)
+    return 1;
+  HFONT font = CreateFontW(16, 0, 0, 0, FW_NORMAL, 0, 0, 0, DEFAULT_CHARSET,
+                           0, 0, 0, FF_MODERN, face);
+  WORD idx = 0;
+  int ok = 1;
+  if (font) {
+    HGDIOBJ old = SelectObject(dc, font);
+    if (GetGlyphIndicesW(dc, &ch, 1, &idx, GGI_MARK_NONEXISTING_GLYPHS) == 1)
+      ok = idx != 0xffff;
+    SelectObject(dc, old);
+    DeleteObject(font);
+  }
+  DeleteDC(dc);
+  return ok;
+}
+
+/* Raster fonts cannot draw UTF-8 box drawing or CJK; switch the console to
+ * a TrueType font of the same height while the TUI runs. */
+static void win_console_font(int on) {
+  HANDLE h = GetStdHandle(STD_OUTPUT_HANDLE);
+  if (!on) {
+    if (g_con_font_saved)
+      SetCurrentConsoleFontEx(h, FALSE, &g_con_font);
+    g_con_font_saved = 0;
+    return;
+  }
+  CONSOLE_FONT_INFOEX f = {.cbSize = sizeof f};
+  if (!GetCurrentConsoleFontEx(h, FALSE, &f))
+    return;
+  if (!(f.FontFamily & TMPF_TRUETYPE)) {
+    g_con_font = f;
+    CONSOLE_FONT_INFOEX tt = {.cbSize = sizeof tt};
+    tt.dwFontSize.Y = f.dwFontSize.Y > 0 ? f.dwFontSize.Y : 16;
+    tt.FontFamily = FF_MODERN | TMPF_TRUETYPE;
+    tt.FontWeight = FW_NORMAL;
+    wcscpy(tt.FaceName, GetACP() == 936 ? L"NSimSun" : L"Consolas");
+    if (!SetCurrentConsoleFontEx(h, FALSE, &tt))
+      return;
+    g_con_font_saved = 1;
+    f = tt;
+  }
+  if (!getenv("WT_SESSION") && !win_font_has(f.FaceName, 0x2580))
+    g_logo_text = 1;
+}
+#endif
+
+#define MOUSE_RUN_MAX 16
+/* getmouse() hands out a run of queued events newest first (the Windows
+ * console driver queues press, motion and release together); returns them
+ * oldest first. */
+static int get_mouse_run(MEVENT *out, int max) {
+  int n = 0;
+  while (n < max && getmouse(&out[n]) == OK)
+    n++;
+  for (int i = 0; i < n / 2; i++) {
+    MEVENT tmp = out[i];
+    out[i] = out[n - 1 - i];
+    out[n - 1 - i] = tmp;
+  }
+  return n;
+}
+
 static void apply_mouse(const tui_t *t) {
   mousemask(t->mouse_on ? (mmask_t)(ALL_MOUSE_EVENTS | REPORT_MOUSE_POSITION)
                         : 0,
             NULL);
   mouseinterval(0);
-#ifdef NCURSES_VERSION
+#ifdef _WIN32
+  win_console_mouse(t->mouse_on);
+#elif defined(NCURSES_VERSION)
   /* ncurses only asks for presses and releases (1000). 1002 also reports
    * motion while a button is held, for drag selection; terminals treat it as
    * replacing 1000, so it goes after mousemask and is turned off explicitly. */
@@ -2869,8 +2978,8 @@ static void layout(tui_t *t) {
     int top = (t->rows - 1 - block) / 2;
     t->in_y = clampi(top + LOGO_H + 1, 0, t->rows - 1 - t->in_h);
     t->log_x = t->log_y = 0;
-    t->logw = newwin(t->rows - 1, t->cols, 0, 0);
-    t->status = newwin(1, t->cols - 2, t->rows - 1, 1);
+    t->logw = tui_newwin(t->rows - 1, t->cols, 0, 0);
+    t->status = tui_newwin(1, t->cols - 2, t->rows - 1, 1);
   } else {
     int mw = t->cols - t->side_w;
     t->in_y = t->rows - 1 - t->in_h;
@@ -2885,14 +2994,14 @@ static void layout(tui_t *t) {
       t->todo_rows = 0;
       log_h = t->in_y - t->log_y > 0 ? t->in_y - t->log_y : 1;
     }
-    t->logw = newwin(log_h, mw - 2, t->log_y, 1);
+    t->logw = tui_newwin(log_h, mw - 2, t->log_y, 1);
     if (t->todo_rows)
-      t->todow = newwin(t->todo_rows, mw - 2, t->log_y + log_h, 1);
-    t->status = newwin(1, mw - 2, t->rows - 1, 1);
+      t->todow = tui_newwin(t->todo_rows, mw - 2, t->log_y + log_h, 1);
+    t->status = tui_newwin(1, mw - 2, t->rows - 1, 1);
     if (t->side_w)
-      t->side = newwin(t->rows, t->side_w, 0, mw);
+      t->side = tui_newwin(t->rows, t->side_w, 0, mw);
   }
-  t->input = newwin(t->in_h, t->in_w, t->in_y, t->in_x);
+  t->input = tui_newwin(t->in_h, t->in_w, t->in_y, t->in_x);
   if (HAS_COLOR()) {
     wbkgdset(t->logw, COLOR_PAIR(CP_PANEL));
     wbkgdset(t->status, COLOR_PAIR(CP_PANEL));
@@ -3495,7 +3604,7 @@ static int picker_run(tui_t *t, const char *title, char items[][128], int n,
       redraw_all(t); /* uncover what a larger dialog hid */
     last_dh = dh;
     last_dw = dw;
-    dlg = newwin(dh, dw, dy, dx);
+    dlg = tui_newwin(dh, dw, dy, dx);
     if (!dlg)
       break;
     keypad(dlg, TRUE);
@@ -3549,9 +3658,14 @@ static int picker_run(tui_t *t, const char *title, char items[][128], int n,
         layout(t);
         redraw_all(t);
       } else if (wch == KEY_MOUSE) {
-        MEVENT ev;
-        if (getmouse(&ev) != OK)
+        MEVENT evs[MOUSE_RUN_MAX], ev;
+        int ne = get_mouse_run(evs, MOUSE_RUN_MAX), k0 = ne - 1;
+        if (ne == 0)
           continue;
+        for (int i = 0; i < ne; i++)
+          if (evs[i].bstate & (BUTTON1_PRESSED | BUTTON1_CLICKED))
+            k0 = i; /* a click anywhere in the run wins over its release */
+        ev = evs[k0];
         if (ev.bstate & BUTTON4_PRESSED) {
           if (sel > 0)
             sel--;
@@ -4301,6 +4415,34 @@ static void cmd_tools(tui_t *t, char *arg, int *quit) {
   }
 }
 
+static void cmd_sandbox(tui_t *t, char *arg, int *quit) {
+  (void)quit;
+  if (arg && strcmp(arg, "reset-labels") == 0) {
+    char *rep = NULL;
+    int n = cst_sandbox_reset_labels(&rep);
+    if (rep && rep[0])
+      push_lines(t, "  ", rep);
+    push_system_line(t, n < 0   ? "(some labels could not be restored; "
+                                  "they stay listed)"
+                        : n == 0 ? "(no labeled directories)"
+                                 : "(labels restored)");
+    free(rep);
+    return;
+  }
+  int sk = cst_sandbox_probe();
+  push_system_line(t, "Shell sandbox: %s",
+                   sk == CST_SANDBOX_NONE ? "none (rule-based approval)"
+                                          : cst_sandbox_name(sk));
+  char *l = cst_sandbox_labels();
+  if (l) {
+    push_system_line(t, "Labeled Low integrity (writable by sandboxed "
+                        "commands):");
+    push_lines(t, "  ", l);
+    push_system_line(t, "/sandbox reset-labels restores their old labels");
+    free(l);
+  }
+}
+
 static void cmd_permissions(tui_t *t, char *arg, int *quit) {
   (void)quit;
   cst_perms_t *p = cst_agent_perms(t->agent);
@@ -4537,7 +4679,7 @@ static void cmd_export(tui_t *t, char *arg, int *quit) {
     *sl = 0;
     os_mkdir_p(dir, 0755);
   }
-  FILE *fp = fopen(path, "w");
+  FILE *fp = fopen(path, "wb");
   if (!fp) {
     push_system_line(t, "Error: cannot write %s", path);
     return;
@@ -4569,9 +4711,19 @@ static void cmd_export(tui_t *t, char *arg, int *quit) {
   push_system_line(t, "(exported to %s)", path);
 }
 
+#ifdef _WIN32
+#define COPY_VIA "clipboard"
+#else
+#define COPY_VIA "OSC 52"
+#endif
+
 /* Puts text on the terminal's clipboard; returns the bytes sent, 0 on
  * failure. */
 static size_t osc52_copy(const char *text, size_t n) {
+#ifdef _WIN32
+  if (os_clipboard_set(text, n) == 0)
+    return n; /* conhost has no OSC 52 */
+#endif
   static const char b64[] =
       "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
   if (n > 75000)
@@ -4614,8 +4766,8 @@ static void cmd_copy(tui_t *t, char *arg, int *quit) {
   }
   size_t n = osc52_copy(text, strlen(text));
   if (n)
-    push_system_line(t, "(copied %zu bytes of the last reply via OSC 52 — the "
-                        "terminal must allow clipboard access)", n);
+    push_system_line(t, "(copied %zu bytes of the last reply via " COPY_VIA
+                        " — the terminal must allow clipboard access)", n);
 }
 
 static void cmd_init(tui_t *t, char *arg, int *quit) {
@@ -4945,6 +5097,8 @@ static const slash_cmd_t SLASH[] = {
      cmd_tools},
     {"permissions", "perms", "[reset]", "show saved always-allow rules", 1,
      cmd_permissions},
+    {"sandbox", "", "[reset-labels]", "shell sandbox and labeled folders", 1,
+     cmd_sandbox},
     {"approval", "", "[ask|auto|yolo]", "how tools get approved (Shift+Tab)",
      1, cmd_approval},
     {"yolo", "", "", "toggle approving everything", 1, cmd_yolo},
@@ -5530,7 +5684,7 @@ static void sel_copy(tui_t *t) {
     for (size_t i = 0; i < b.n; i++)
       chars += ((unsigned char)b.s[i] & 0xC0) != 0x80;
     char msg[96];
-    snprintf(msg, sizeof(msg), "Copied %zu characters (OSC 52)", chars);
+    snprintf(msg, sizeof(msg), "Copied %zu characters (" COPY_VIA ")", chars);
     set_status(t, msg);
     draw_status(t);
   }
@@ -6187,6 +6341,21 @@ static void insert_newline(tui_t *t) {
 }
 
 /* Paste mode: keep newlines/tabs literally; redraw once at the end. */
+#ifdef _WIN32
+static int win_key_pending(void) {
+  INPUT_RECORD rec[32];
+  DWORD n = 0;
+  HANDLE h = GetStdHandle(STD_INPUT_HANDLE);
+  if (!PeekConsoleInputW(h, rec, 32, &n))
+    return 0;
+  for (DWORD i = 0; i < n; i++)
+    if (rec[i].EventType == KEY_EVENT && rec[i].Event.KeyEvent.bKeyDown &&
+        rec[i].Event.KeyEvent.uChar.UnicodeChar)
+      return 1;
+  return 0;
+}
+#endif
+
 static void paste_char(tui_t *t, wint_t wch) {
   if (wch == 13) {
     input_put_byte(t, '\n');
@@ -6207,20 +6376,31 @@ static void paste_char(tui_t *t, wint_t wch) {
 }
 
 int cst_tui_run(cst_agent_t *agent) {
+#ifdef _WIN32
+  setlocale(LC_ALL, ".UTF-8");
+#else
   if (!setlocale(LC_ALL, ""))
     setlocale(LC_ALL, "C.UTF-8");
+#endif
 #ifndef _WIN32
   if (!getenv("ESCDELAY"))
     setenv("ESCDELAY", "25", 0);
 #endif
 
+#ifdef _WIN32
+  win_console_font(1);
+#endif
   initscr();
+#ifdef _WIN32
+  idcok(stdscr, FALSE);
+#endif
   raw(); /* Ctrl+C/Ctrl+Z reach us as keys instead of signals */
   noecho();
   keypad(stdscr, TRUE);
   curs_set(1);
   theme_init();
-#ifdef NCURSES_VERSION
+#if defined(NCURSES_VERSION) && !defined(_WIN32)
+  /* the Windows console driver reads key events, not VT sequences */
   define_key("\033[200~", KEY_PASTE_BEGIN);
   define_key("\033[201~", KEY_PASTE_END);
   printf("\033[?2004h");
@@ -6375,6 +6555,18 @@ int cst_tui_run(cst_agent_t *agent) {
     if (t.sel_state == SEL_SHOWN &&
         !(rc == KEY_CODE_YES && (wch == KEY_MOUSE || wch == KEY_RESIZE)))
       sel_clear(&t);
+#ifdef _WIN32
+    /* The console has no bracketed paste: an Enter with more keys already
+     * queued is a pasted line break, not a send. */
+    if (rc == OK && !t.in_paste && (wch == 10 || wch == 13) &&
+        win_key_pending()) {
+      paste_char(&t, wch);
+      input_changed(&t);
+      after_edit(&t);
+      draw_input(&t);
+      continue;
+    }
+#endif
 
     if (!t.in_paste &&
         !(rc == KEY_CODE_YES &&
@@ -6453,12 +6645,13 @@ int cst_tui_run(cst_agent_t *agent) {
         continue;
       }
       if (wch == KEY_MOUSE) {
-        MEVENT ev;
-        if (getmouse(&ev) == OK) {
-          if (on_mouse(&t, &ev, busy) == -2)
+        MEVENT evs[MOUSE_RUN_MAX];
+        int ne = get_mouse_run(evs, MOUSE_RUN_MAX);
+        for (int i = 0; i < ne; i++)
+          if (on_mouse(&t, &evs[i], busy) == -2)
             goto out;
+        if (ne)
           draw_input(&t); /* keep the terminal cursor in the box */
-        }
         continue;
       }
       int wdir;
@@ -6667,7 +6860,11 @@ out:
     usleep(100000); /* let a /models probe finish before curl cleanup */
 
   tui_free(&t);
-#ifdef NCURSES_VERSION
+#ifdef _WIN32
+  if (g_con_in_saved)
+    win_console_mouse(0);
+  win_console_font(0);
+#elif defined(NCURSES_VERSION)
   kitty_restore();
   printf("\033[?1002l\033[?2004l");
   fflush(stdout);