When a coderai broker provider's worker is offline, requests are held and
retried while it warms up. The hold window was hardcoded (10s x 3 = 30s).
Expose it per provider via coderai_config:
- broker_queue_timeout_seconds: total hold time (0 disables holding)
- broker_warmup_wait_seconds: poll interval between retries
- broker_max_warmup_waits: explicit retry count (when no queue timeout)

Defaults preserve prior behavior. Applied to both warm-up retry loops.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>