Why: Q3 WP4 requires A2A 1.0 interop from zero: publish this team's
capabilities as an Agent Card and consume remote agents as squad.Executors
with the A2A task state machine mapped onto ExecResult.
Evidence: adapters/a2a conformance with a local fake A2A server (both
directions): card build from role/blueprint registries, well-known JSON
serving, FetchCard fail-closed validation, message/send -> tasks/get
polling through submitted/working -> completed with TextPart/FilePart
artifacts mapped to patches/targets, failed/canceled/rejected/input-required
mapped to Success=false fail-closed (no cross-process hold), direct Message
result, JSON-RPC protocol and ctx-cancel error propagation. Module green
with -race; squad root suite unaffected (SELF). CI authoritative (GATE)
for the root module; the adapter module follows the adapters/intent and
adapters/native separate-go.mod precedent.
Impact: new module agent-squad/adapters/a2a (card.go, executor.go); no
changes to the squad root module.
Refs: Q3 plan WP4 (2026-10-07-agent-stack-q2q3-plans.md); task card
.task/feature-agent-stack-q3.md
