- New website/docs/user-guide/messaging/a2a.md: when/where to use A2A
(cross-machine, specialist peers, being callable) vs delegation/kanban
for same-machine multi-agent; enable, outbound tools, inbound surface,
security model, env reference, quick test, troubleshooting. Registered
in sidebars.ts and the messaging index.
- README/DESIGN/plugin.yaml/protocol.py prose updated to name the A2A
v1.0 canonical discovery path /.well-known/agent-card.json (the code
already served both; only the docs lagged).