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

CMakeLists.txt

@@ -8,6 +8,32 @@ option(CST_BUILD_TUI "Build ncurses/PDCurses TUI" ON)
 option(CST_NATIVE_ARCH "Pass -march=native to sashidown" OFF)
 option(CST_BUNDLE_BUSYBOX "Install placeholder/scripts for busybox beside binary" ON)
 
+if(WIN32)
+  enable_language(RC)
+  # Cross builds link libgcc/winpthreads/curl statically; MSYS2's curl is a DLL.
+  if(CMAKE_CROSSCOMPILING)
+    set(_CST_STATIC_DEFAULT ON)
+  else()
+    set(_CST_STATIC_DEFAULT OFF)
+  endif()
+  option(CST_WIN_STATIC "Link Windows executables with -static" ${_CST_STATIC_DEFAULT})
+endif()
+
+# Windows: UTF-8 manifest (activeCodePage, longPathAware) and version resource
+# on every executable, so tests run with the same process code page as the app.
+function(cst_win_exe t)
+  if(NOT WIN32)
+    return()
+  endif()
+  target_sources(${t} PRIVATE "${CMAKE_CURRENT_SOURCE_DIR}/res/windows/cst-agent.rc")
+  target_include_directories(${t} PRIVATE
+    "${CMAKE_CURRENT_SOURCE_DIR}/include" "${CMAKE_CURRENT_SOURCE_DIR}/res/windows")
+  target_compile_definitions(${t} PRIVATE _WIN32_WINNT=0x0A00)
+  if(CST_WIN_STATIC)
+    target_link_options(${t} PRIVATE -static)
+  endif()
+endfunction()
+
 set(SD_DIR "${CMAKE_CURRENT_SOURCE_DIR}/vendor/sashidown")
 if(CST_NATIVE_ARCH)
   set(_SD_MAKE_EXTRA CST_NATIVE_ARCH=1)
@@ -15,6 +41,9 @@ else()
   set(_SD_MAKE_EXTRA "")
 endif()
 
+# sashidown has a plain Makefile; CMAKE_MAKE_PROGRAM may be ninja.
+find_program(CST_MAKE NAMES make gmake mingw32-make REQUIRED)
+
 # Separate archive for MinGW so Linux host builds keep libsashidown.a
 if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
   set(SASHIDOWN_A "${SD_DIR}/libsashidown-mingw.a")
@@ -26,19 +55,19 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
   set(_MINGW_RANLIB "${CMAKE_RANLIB}")
   add_custom_command(
     OUTPUT "${SASHIDOWN_A}"
-    COMMAND ${CMAKE_MAKE_PROGRAM} -C "${SD_DIR}" clean
-    COMMAND ${CMAKE_MAKE_PROGRAM} -C "${SD_DIR}" libsashidown.a
+    COMMAND ${CST_MAKE} -C "${SD_DIR}" clean
+    COMMAND ${CST_MAKE} -C "${SD_DIR}" libsashidown.a
             CC=${CMAKE_C_COMPILER} AR=${_MINGW_AR} RANLIB=${_MINGW_RANLIB}
     COMMAND ${CMAKE_COMMAND} -E copy_if_different
             "${SD_DIR}/libsashidown.a" "${SASHIDOWN_A}"
-    COMMAND ${CMAKE_MAKE_PROGRAM} -C "${SD_DIR}" clean
+    COMMAND ${CST_MAKE} -C "${SD_DIR}" clean
     COMMENT "Building libsashidown for MinGW"
     VERBATIM)
 else()
   set(SASHIDOWN_A "${SD_DIR}/libsashidown.a")
   add_custom_command(
     OUTPUT "${SASHIDOWN_A}"
-    COMMAND ${CMAKE_MAKE_PROGRAM} -C "${SD_DIR}" libsashidown.a CC=${CMAKE_C_COMPILER} ${_SD_MAKE_EXTRA}
+    COMMAND ${CST_MAKE} -C "${SD_DIR}" libsashidown.a CC=${CMAKE_C_COMPILER} ${_SD_MAKE_EXTRA}
     COMMENT "Building libsashidown.a"
     VERBATIM)
 endif()
@@ -54,6 +83,7 @@ set(CST_CORE_SOURCES
   src/util.c
   src/ctl_parse.c
   src/os_compat.c
+  src/os_win.c
   src/sandbox.c
   src/sandbox_exec.c
   src/keymap.c
@@ -82,6 +112,14 @@ set(CST_CORE_SOURCES
   src/models.c
   src/metrics.c
 )
+if(WIN32)
+  # MinGW has no <regex.h>: musl's TRE engine, UTF-8 aware (vendor/tre-regex)
+  include_directories(vendor/tre-regex)
+  list(APPEND CST_CORE_SOURCES
+    vendor/tre-regex/regcomp.c vendor/tre-regex/regexec.c
+    vendor/tre-regex/regerror.c vendor/tre-regex/tre-mem.c)
+endif()
+
 set(CST_SOURCES ${CST_CORE_SOURCES} src/main.c)
 
 if(CST_BUILD_TUI)
@@ -92,6 +130,7 @@ endif()
 
 add_executable(cst-agent ${CST_SOURCES})
 add_dependencies(cst-agent sashidown)
+cst_win_exe(cst-agent)
 
 target_include_directories(cst-agent PRIVATE
   include
@@ -113,9 +152,26 @@ if(NOT WIN32)
   target_link_libraries(cst-agent PRIVATE m)
 endif()
 
-if(CST_BUILD_TUI)
+set(CST_WIN_CURSES "ncurses" CACHE STRING "Windows TUI backend: ncurses or pdcurses")
+set_property(CACHE CST_WIN_CURSES PROPERTY STRINGS ncurses pdcurses)
+if(CST_BUILD_TUI AND WIN32 AND CST_WIN_CURSES STREQUAL "ncurses")
+  # ncursesw built by scripts/build_third_party_mingw.sh ncurses (or MSYS2's
+  # mingw-w64-ucrt-x86_64-ncurses); headers live in include/ncursesw.
+  find_path(NCURSESW_INCLUDE_DIR ncurses.h PATH_SUFFIXES ncursesw include/ncursesw)
+  find_library(NCURSESW_LIBRARY NAMES ncursesw)
+  if(NOT NCURSESW_INCLUDE_DIR OR NOT NCURSESW_LIBRARY)
+    message(FATAL_ERROR "CST_WIN_CURSES=ncurses needs ncursesw "
+      "(scripts/build_third_party_mingw.sh ncurses), or -DCST_WIN_CURSES=pdcurses")
+  endif()
+  # ncurses.h includes <ncursesw/ncurses_dll.h>, so the parent is needed too
+  get_filename_component(NCURSESW_PARENT_DIR ${NCURSESW_INCLUDE_DIR} DIRECTORY)
+  target_include_directories(cst-agent PRIVATE ${NCURSESW_INCLUDE_DIR} ${NCURSESW_PARENT_DIR})
+  target_link_libraries(cst-agent PRIVATE ${NCURSESW_LIBRARY})
+  target_compile_definitions(cst-agent PRIVATE CST_USE_NCURSES=1 NCURSES_STATIC=1 NCURSES_WIDECHAR=1)
+  message(STATUS "TUI: ncursesw (${NCURSESW_LIBRARY})")
+elseif(CST_BUILD_TUI)
   if(WIN32)
-    # Prefer PDCurses (pdcurses / curses). Users may set PDCurses_ROOT.
+    # PDCurses (pdcurses / curses). Users may set PDCurses_ROOT.
     # PATH_SUFFIXES also covers the layout MSYS2's mingw-w64-pdcurses uses,
     # which puts the headers under include/pdcurses/ rather than include/.
     find_path(PDCURSES_INCLUDE_DIR curses.h
@@ -156,7 +212,7 @@ endif()
 if(CMAKE_SYSTEM_NAME STREQUAL "Windows" OR WIN32)
   # curl Schannel + networking; winmm is needed by PDCurses (PlaySoundW)
   target_link_libraries(cst-agent PRIVATE
-    ws2_32 crypt32 secur32 bcrypt advapi32 winmm)
+    ws2_32 crypt32 secur32 bcrypt advapi32 user32 gdi32 winmm)
 endif()
 
 # --- tests ---
@@ -166,7 +222,11 @@ set(_CST_SMALL_TESTS test_ctl_frontier test_ctl_heredoc test_json_baseline
     test_markdown)
 foreach(t ${_CST_SMALL_TESTS})
   if(t STREQUAL test_textsel)
-    add_executable(${t} tests/${t}.c src/textsel.c)
+    add_executable(${t} tests/${t}.c src/textsel.c src/os_compat.c src/os_win.c
+      src/util.c)
+    if(WIN32)
+      target_link_libraries(${t} PRIVATE advapi32 user32)
+    endif()
   elseif(t STREQUAL test_markdown)
     add_executable(${t} tests/${t}.c)
     target_include_directories(${t} PRIVATE "${SD_DIR}/include")
@@ -186,6 +246,7 @@ foreach(t ${_CST_SMALL_TESTS})
   if(NOT WIN32)
     target_link_libraries(${t} PRIVATE m)
   endif()
+  cst_win_exe(${t})
   add_test(NAME ${t} COMMAND ${t} WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}")
 endforeach()
 
@@ -194,7 +255,8 @@ foreach(t test_llm_body test_sse_decode test_apply_patch test_session_roundtrip
           test_shell test_diff test_tools_fs test_registry
           test_undo test_config test_models test_sandbox
           test_keymap test_shell_compact test_skills
-          test_plugins test_mcp test_subagent)
+          test_plugins test_mcp test_subagent test_lowil
+          test_win_utf8 test_os_dir)
   add_executable(${t} tests/${t}.c ${CST_CORE_SOURCES})
   target_include_directories(${t} PRIVATE include "${CJSON_DIR}")
   target_compile_definitions(${t} PRIVATE _GNU_SOURCE)
@@ -202,8 +264,9 @@ foreach(t test_llm_body test_sse_decode test_apply_patch test_session_roundtrip
   if(NOT WIN32)
     target_link_libraries(${t} PRIVATE m)
   else()
-    target_link_libraries(${t} PRIVATE ws2_32 crypt32 secur32 bcrypt advapi32)
+    target_link_libraries(${t} PRIVATE ws2_32 crypt32 secur32 bcrypt advapi32 user32)
   endif()
+  cst_win_exe(${t})
   add_test(NAME ${t} COMMAND ${t} WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}")
 endforeach()