fix: spawn lock + dead port reconnect

[four-bytes-robby]

Adds spawn lock to prevent duplicate bus binaries. scheduleReconnect now re-reads port file before retry.

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Summary by cubic

Prevents duplicate bus processes during concurrent connects and fixes reconnects when the bus restarts on a new port.

• Bug Fixes
  • Added a module-level spawn lock in BusClient so concurrent connect() calls share one in-flight spawn; extracted spawnBus() for clean lock release.
  • BusTui scheduleReconnect() now re-reads the port via discoverPort before retrying, avoiding dead cached ports after crashes/restarts.

^{Written for commit b96489a. Summary will update on new commits.}

Summary by CodeRabbit

• Bug Fixes
  • Improved concurrent connection request handling to prevent spawning multiple duplicate bus processes when multiple simultaneous connection attempts occur.
  • Enhanced reconnection logic to dynamically re-discover the bus port before attempting connections, instead of relying on previously cached port values. This ensures more reliable reconnection behavior when the bus port may have changed.

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

Walkthrough

Walkthrough

Two bus connection fixes are applied: bus-client.ts gains a module-level spawnLock promise to deduplicate concurrent connect() auto-start calls so only one bus process is spawned, and bus-tui.ts updates scheduleReconnect to reset the cached port and re-run discoverPort before retrying open().

Changes

Bus connection robustness

Layer / File(s)	Summary
spawnLock: serialize concurrent bus startup src/bus-client.ts	Adds a module-scoped spawnLock: Promise<void> | null variable. startBus() returns the in-flight lock when one exists; otherwise it assigns spawnLock to the result of a new spawnBus() call and clears the lock in .finally() after the spawn attempt settles.
BusTui reconnect: reset port and re-discover src/bus-tui.ts	In scheduleReconnect, resets this.port to 0 and awaits discoverPort(2000) before calling open(). If discovery throws, this.port stays 0 and open() is called anyway to handle the failure and keep the retry loop running.

Estimated code review effort

3 (Moderate) | ~20 minutes

Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix: spawn lock + dead port reconnect' directly and specifically summarizes the two main changes: adding a spawn lock mechanism and fixing port re-discovery on reconnect.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Finishing Touches

Generate docstrings

• Create stacked PR
• Commit on current branch

Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/bus-spawn-reconnect

Simplify code

• Create PR with simplified code
• Commit simplified code in branch fix/bus-spawn-reconnect

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