fix: clean up orphaned bridge and MCP child processes (#1724)

[Yeachan-Heo]

Summary

• add parent-exit detection to the Python gyoshu bridge so orphaned bridge processes self-terminate
• extend standalone MCP shutdown handling to react to parent PID changes and clean up owned bridge sessions
• stop omc hud --watch loops when shutdown/parent-exit is detected and add regression coverage

Testing

• npx tsc --noEmit
• npx vitest run src/mcp/__tests__/standalone-shutdown.test.ts src/cli/__tests__/hud-watch.test.ts src/tools/python-repl/__tests__/bridge-manager-cleanup.test.ts src/cli/__tests__/launch.test.ts src/__tests__/standalone-server.test.ts src/hooks/session-end/__tests__/session-end-bridge-cleanup.test.ts src/hooks/session-end/__tests__/python-repl-cleanup.test.ts
• npm run build

[github-actions]

⚠️ Large PR Alert

This PR has 1597 additions and 563 deletions across 30 files.

Consider breaking it into smaller PRs for easier review.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Reorder shutdown steps to avoid 5s force-exit cutoff

gracefulShutdown now awaits cleanupOwnedBridgeSessions() before disconnectAllLsp() while a hard setTimeout(() => process.exit(1), 5000) is already running, so a single unresponsive bridge can consume the entire deadline (the bridge cleanup path escalates over multiple waits in killBridgeWithEscalation) and force-exit the process before LSP/server cleanup runs. In that scenario this change can still leave orphaned LSP children despite entering the shutdown handler.

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[chatgpt-codex-connector]

Parse parent poll interval defensively

The module-level float(os.environ.get("OMC_PARENT_POLL_INTERVAL_MS", "1000")) conversion throws ValueError for any non-numeric env value (for example an empty string), which aborts bridge startup before request handling begins. Because this runs at import time, one malformed environment variable can break all Python bridge launches instead of falling back to the default interval.

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