Initial CST-Agent: portable Linux/Termux/Windows coding agent.

Vendored sashidown, OpenAI-compatible env (OPENAI_*), and bootstrap scripts.

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

scripts/run_windows.bat

@@ -0,0 +1,27 @@
+@echo off
+REM Run ON Windows after copying dist/windows-x86_64 (or a full git checkout + MSYS2 build).
+REM This script only documents env + launch; prefer bootstrap_windows.sh on Linux for cross-build.
+
+setlocal
+if "%OPENAI_API_KEY%"=="" if "%CST_API_KEY%"=="" (
+  echo Set OPENAI_API_KEY or CST_API_KEY first. See docs\env_openai.md
+  echo Example:
+  echo   set OPENAI_API_KEY=sk-...
+  echo   set OPENAI_BASE_URL=https://api.openai.com/v1
+  echo   set OPENAI_MODEL=gpt-4.1-mini
+  exit /b 1
+)
+
+if not exist cst-agent.exe (
+  echo cst-agent.exe not found in %CD%
+  echo Copy dist\windows-x86_64\* here, or build with MSYS2/MinGW.
+  exit /b 1
+)
+
+if not exist busybox.exe (
+  echo WARNING: busybox.exe missing — run_shell may fail. Place busybox.exe beside cst-agent.exe
+)
+
+echo Launching CST-Agent...
+cst-agent.exe --workspace .
+endlocal