fix: 修复 Windows 终端兼容性

[yg2224]

Summary

• 修复 Windows 本地 runtime 的命令包装，按 PowerShell 处理 cwd 和 env
• 修正 PowerShell non-terminating error 的退出码判定，避免失败被误报为成功
• 按 provider 回退 terminal 默认 cwd，避免远端 sandbox 落回宿主机路径

Test Plan

• uv run pytest tests/test_capability_async.py tests/test_chat_session.py tests/test_runtime.py tests/test_terminal.py tests/test_terminal_persistence.py -q

[shuxueshuxue]

I reviewed this patch against current dev. Two issues look real before merge:

1. core/tools/command/bash/executor.py and core/tools/command/zsh/executor.py

   • the new Windows guard makes execute() return ExecuteResult(exit_code=127, ...), but execute_async() raises RuntimeError for the same unsupported condition.
   • that splits one platform constraint into two different contracts depending on call path.

2. sandbox/terminal.py + storage/providers/{sqlite,supabase}/terminal_repo.py

   • the new default cwd fallback now depends on the host process cwd when initial_cwd is absent or provider lookup fails.
   • that means terminal truth can drift with the backend's launch directory instead of a stable terminal/workspace invariant.

I would not merge this as-is. The Windows compatibility direction is fine, but these two contract changes need tightening first.