feat: add development environment launchers

[LIUXIN557]

Summary

• add target-specific Web, Desktop, and TUI development launchers for Windows, macOS, and Linux
• discover compatible builds across Git worktrees, rebuild incrementally, and refresh Web assets before launch
• initialize the Visual Studio C++ environment automatically for Windows batch launchers
• add focused launcher tests and the approved OpenSpec change

Verification

• python -m unittest tests/scripts/dev_environment_test.py
• python -m py_compile scripts/dev_environment.py tests/scripts/dev_environment_test.py
• openspec validate add-development-environment-launcher --strict
• git diff --check
• end-to-end Windows validation: Web daemon returned HTTP 200, Desktop process started, and TUI opened in a new terminal process