Replace blocking domain pool with non-blocking architecture:
- Main accept loop handles ALL connections immediately
- Cached responses: served in microseconds from main loop (no queuing)
- Static files: served immediately from main loop
- Cache misses: queued to render worker pool (domain workers)
- Socket timeouts (5s recv, 10s send) prevent connection hangs
- TCP backlog increased to 1024
No more connection resets under load. 22/26 Playwright tests pass
(4 failures from stale worktree test copies, 0 from main tree).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>