OptimizedNodeBridge init should be concurrency-safe

[bbopen]

Summary

OptimizedNodeBridge.init() does not guard against concurrent calls. Multiple callers can trigger overlapping init() invocations, spawning more than minProcesses and running warmups multiple times.

Failure mode

• Two callers invoke init() concurrently.
• Both loops see processPool.length < minProcesses and spawn extra workers.
• Warmup commands run multiple times.

Evidence

• src/runtime/optimized-node.ts init() has no initPromise guard (unlike NodeBridge).

Proposed fix

• Add an initPromise guard to make init() idempotent and safe under concurrency.
• Ensure warmup runs once per initialization.

Acceptance criteria

• Concurrent init() calls do not overspawn workers.
• Warmup commands run once.
• Add a test that calls init() concurrently and verifies pool size.

[bbopen]

✅ Resolved in PR #136: refactor: unify NodeBridge and OptimizedNodeBridge (ADR-0001)

The unified NodeBridge now uses initPromise deduplication to ensure concurrent init() calls don't spawn duplicate workers. Multiple concurrent calls to init() will await the same initialization promise.