Fixes 6 issues flagged by Cursor Bugbot on PR #188:
1. sessionFileMatchesCwd reads only first 4 KB via open()+read() instead of
loading entire rollout file into memory (Medium)
2. Binary resolution race condition: added promise guard to prevent
concurrent resolveCodexBinary() calls (Low)
3. Concurrent connect() calls: added connecting guard to prevent
orphaned child processes (High)
4. connect() failure cleanup: wrap initialize() in try/catch that
calls close() on failure (Medium)
5. readline cleanup on process exit/error: close readline in both
handleProcessExit and handleProcessError (Medium)
6. stderr pipe drain: call stderr.resume() to prevent child blocking
when stderr buffer fills (High)
All 177 tests pass, typecheck clean.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
4e7129d50d