Replace busy-wait with Atomics

[tembo]

Summary

Replaced CPU-intensive busy-wait loop with Atomics.wait() in lock acquisition retry logic. The previous implementation used a spin loop (while (Date.now() < until)) that burned CPU cycles during the 50ms retry delay. Now uses Atomics.wait() with a SharedArrayBuffer to properly yield the thread during sleep.

Changes:

• Added sleepBuffer using SharedArrayBuffer and Int32Array for Atomics.wait()
• Implemented sleepSync() helper function that uses Atomics.wait() for efficient sleeping
• Replaced busy-wait loop in acquireLock() with sleepSync(LOCK_RETRY_MS) call

Additional findings documented in .beads/issues.jsonl:

• Race condition in lock file handling (t2p-scan01)
• Infinite recursion risk in review.ts (t2p-scan02)
• Unsafe process.env.HOME access (t2p-scan03)
• Content analyzer validation bug (t2p-scan04)
• Template substitution using replace() instead of replaceAll() (t2p-scan05)

Want tembo to make any changes? Add a review or comment with @tembo and i'll get back to work!

[tembo]

Requesting review from @ryw who has experience with the following files modified in this PR:

• package-lock.json
• .beads/issues.jsonl
• src/services/file-system.ts