a2a-market-ucp-broadcast

# a2a-Market UCP Broadcast Define the transport and protocol shell for intent broadcast in UCP. Current status: framework release for registration. Prioritize interoperability contracts over optimization. ## Scope - Build intent payload schema and canonical signing routine. - Broadcast to eligible nodes and track delivery acknowledgements. - Feed response stream into quote intake service. ## Suggested Project Layout - `app/protocol/ucp/intent_message.py` - `app/protocol/ucp/signer.py` - `app/application/services/broadcast_service.py` - `app/infrastructure/ws/ucp_gateway.py` ## Minimum Contracts (MVP P0) 1. `build_intent(payload)` normalizes and version-tags message. 2. `sign_intent(intent, private_key)` returns detached signature object. 3. `broadcast(intent_id, target_nodes)` returns dispatch receipt ids. 4. `collect_acks(intent_id, timeout_ms)` returns per-node ack status. ## Event Mapping - Emit `INTENT_CREATED` before dispatch. - Emit `INTENT_BROADCASTED` after fan-out completes. - Emit `NODE_RESPONDED` when quote/ack arrives. ## Guardrails - Keep canonical JSON serialization deterministic for signing. - Record per-node retry counters and stop after configured threshold. - Attach protocol version in every envelope. ## Implementation Backlog - Add adaptive node selection based on reputation percentile. - Add dead-letter handling for nodes with repeated timeouts. ## Runtime Implementation - Status: implemented in local runtime package. - Primary code paths: - `runtime/src/protocol/ucp-client.js` - `runtime/src/application/market-agent.js` - Validation: covered by `runtime/tests` and `npm test` in `runtime/`.