Keep dashboard chat alive across reconnects

[ljubomirj]

Summary

Keep the dashboard chat session alive across transient browser WebSocket disconnects, such as laptop sleep/wake or network loss.

This changes /api/pty ownership so an abnormal WebSocket close parks the PTY bridge for a bounded reconnect window instead of immediately closing the hermes --tui child. The browser chat tab now retries the PTY WebSocket with bounded exponential backoff and reuses the same stable channel id, so reconnecting can reclaim the running TUI session and its history.

Details

• Add a reconnectable PTY bridge pool keyed by chat channel id.
• Reclaim a parked PTY bridge on reconnect instead of spawning a fresh child.
• Keep abnormal/no-status WebSocket closes (1006/1005) alive for reconnect, while intentional page teardown (1000) still closes normally.
• Wait for WebSocket.onopen before sending resize data or announcing reconnect success.
• Extend regression coverage for abnormal disconnect/reclaim behavior.
• Relax TUI gateway orphan reaping so short sleep/wake gaps do not discard active sessions too aggressively.

Validation

• python3 -m py_compile hermes_cli/web_server.py tui_gateway/server.py
• git diff --cached --check
• /Users/ljubomir/hermes-agent-macbook2/.venv/bin/python -m pytest tests/hermes_cli/test_web_server.py -k 'reconnectable or TestPtyWebSocket' -q
• /Users/ljubomir/hermes-agent-macbook2/.venv/bin/python -m pytest tests/test_tui_gateway_server.py -k ws_orphan_reap -q
• /Users/ljubomir/hermes-agent-macbook2/.venv/bin/python -m ruff check hermes_cli/web_server.py tests/hermes_cli/test_web_server.py tui_gateway/server.py
• npm --workspace web run typecheck
• npm --workspace web run build
• npm --workspace web exec eslint -- src/pages/ChatPage.tsx completed with warnings only; no errors.

[teknium1]

Closing this draft — the same keep-alive goal landed on main in #60515 (salvage of #50084): PTY parked across disconnects, reattach with ring-buffer replay, bounded reap. Thanks for working on it — credit noted in the salvage PR.