feat: Hermit 1.1.0 — HERMIT_* env, Tauri desktop shell

Wire hermit_getenv across the engine, rebrand WebUI/systemd/docs, and
add apps/desktop (Tauri 2 + React) with a DeepSeek-Harness-like UI.
Qt app/ is frozen; full libcstcore FFI is scaffolded behind --features engine.

Co-authored-by: Cursor <cursoragent@cursor.com>

include/os_compat.h

@@ -213,6 +213,9 @@ int os_utf8_encode(unsigned long cp, char out[4]);
  * text as GBK and the screen would show mojibake. */
 int os_utf8_decode(const char *s, size_t avail, unsigned long *cp);
 
+/* HERMIT_<suffix> then CST_<suffix>. Never NULL (may be ""). */
+const char *hermit_getenv(const char *suffix);
+
 /* --- libc gaps on Windows ------------------------------------------------
  * MinGW-w64 provides neither strcasestr() (a GNU extension) nor
  * setenv()/unsetenv() (POSIX): they are simply absent from its headers.