Address round-1 review nits: - document why _ocs_capabilities omits the rest of the OCS envelope (Pact V4 allows extra provider-side keys; pin only astrolabe's own block) - use the module-level _BROKER_READY in the broker-source guard instead of re-checking the three env vars inline Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>