Additive plumbing for v0.9.0 daemon spec §4.2/§4.4. Adds two nullable
columns to mesh.message_queue — client_message_id (caller-supplied) and
request_fingerprint (canonical sha256 of the send shape) — and threads
them through the broker:
- handleSend reads them off the wire envelope when present
- queueMessage persists them on the row
- drainForMember projects them onto the push so receiving daemons
can dedupe their local inbox by client_message_id
Columns stay nullable so legacy traffic (launch CLI, dashboard chat)
continues to flow uninterrupted. Sprint 7 (broker hardening) will add
the partial unique index and the client_message_dedupe atomic-accept
table once we're ready to enforce dedupe broker-side.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
