Summary

• add a first A2A config surface for local identity, inbound auth, and named peers
• expose agent-card discovery and authenticated /api/a2a/message endpoints
• add a2a_list_peers and a2a_send built-in tools plus generated docs
• cover config normalization and end-to-end A2A flow with tests

Testing

• cargo fmt --all
• node scripts/generate_docs_artifacts.mjs
• cargo test

Closes #227