fix(tui): join slash worker drain threads

[LeonSGP43]

Summary

• keep explicit references to slash worker stdout/stderr drain threads
• close worker stdio pipes and join both drain threads during worker shutdown
• add a focused regression test for _SlashWorker.close() plus the existing session create/close race guard

Testing

• uv run python --version
• git diff --check
• uv run --extra dev python -m pytest tests/test_tui_gateway_server.py -k "slash_worker_close_joins_drain_threads_and_closes_pipes or session_create_close_race_does_not_orphan_worker"
• uv run --extra dev ruff check tui_gateway/server.py tests/test_tui_gateway_server.py

Notes

• tests/test_tui_gateway_server.py::test_browser_manage_connect_default_local_reports_launch_hint is already failing on an untouched browser-manage path and was treated as unrelated baseline noise for this narrow change.

[alt-glitch]

This was generated by AI during triage.

Duplicate of #53308 — same fix (join _SlashWorker stdout/stderr drain threads on close) for the same issue #53303. #53308 is the earlier open PR (canonical). Linking for the maintainer to pick one.

[tonydwb]

Code Review Summary

Verdict: Approved

Fixes resource leak in _SlashWorker.close() by joining drain threads and closing stdin/stdout/stderr. Clean fix with a dedicated test that verifies thread joining and stream closing.

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Reviewed by Hermes Agent

[teknium1]

Thanks for targeting the remaining slash-worker cleanup gap. The premise is still valid on current main: tui_gateway/server.py:326-327 starts anonymous drain threads and close() ends after stream cleanup at tui_gateway/server.py:391-396, without joining them.

Problems

• The added join loop unconditionally reads self._stdout_thread and self._stderr_thread. Current tests/test_tui_gateway_server.py:8252-8255 constructs _SlashWorker via object.__new__ with only proc, so this change raises AttributeError. The canonical duplicate #53308 recorded and fixed this exact compatibility case in da52fdffb80923bf85efaf94d483584eb427322c using getattr(..., None) guards.

Suggested changes

• Use guarded thread lookup and join only present thread objects, then preserve both the existing zombie/FD test and the new drain-join test.

Automated hermes-sweeper review.

[teknium1]

This unconditionally reads attributes that are absent on the existing object.__new__(server._SlashWorker) fixture in tests/test_tui_gateway_server.py:8252. Use getattr(self, "_stdout_thread", None) / getattr(self, "_stderr_thread", None) and skip None values so close() remains compatible with that regression path.