test: clean up HTTP servers on Windows

[DorianChn]

Summary

• shut down HTTP test servers before joining their threads and closing sockets
• remove Windows WinError 10038 cleanup noise while preserving the existing 38-test coverage
• add a Python 3.9-3.13 GitHub Actions matrix and CLI smoke test

Validation

• python -m unittest discover -s tests -p "test_*.py" -v (38 tests passed)
• Windows run no longer emitted WinError 10038
• CLI allow-path smoke test passed
• git diff --check

[DorianChn]

补充验证（使用 Codex bundled Python runtime，因为当前系统 PATH 没有 python/py）：

• python -m unittest discover -s tests -p "test_*.py" -v ✅ 38 tests passed
• CI 中的 CLI smoke command ✅ returned allowed: true
• 工作区无未提交改动；当前分支仍为 PR test: clean up HTTP servers on Windows #1 的分支

PR #1 目前与 main 无冲突，等待维护者审核/合并。