OpenClaw: serve and delegate A2A tasks

[dimavrem22]

Decisions

• Durability: Persist each receiver delivery before acknowledgement, reconcile the registry first on restart, and then page all submitted tasks.
• Session isolation: Route inbound tasks to exact a2a:{identity}:{context} sessions, capture output without normal channel delivery, and authorize complete, ask-caller, and fail only during the active A2A turn.
• Cancellation: Track every active run for a task so task-addressed cancellation aborts all matching work without affecting another context.
• Delegation continuity: Persist outbound message/retry data before SendMessage, promote it to (identity, RPC origin, context), and inject later task updates into the original OpenClaw session.
• Compatibility: Keep the base SDK range for non-A2A users, while documenting that A2A requires @inkbox/sdk 0.5.6 or newer.

Changes

• Add A2A call, check, reply, and inbound complete/ask/fail tools.
• Subscribe and serve inbound tasks with durable deduplication, context sessions, cancellation, restart recovery, and guarded default completion.
• Add durable caller-side delegation routing and sent-task update injection.
• Update the public tool contract/docs and bump the plugin to 0.2.3.

Related pull requests

• SDK/CLI: Inkbox SDK PR #123
• Hosts: Hermes PR #72, Claude Code PR #45, Codex PR #26, OpenCode PR #9

Merge order

Merge after the paused-contract base PR, backend deployment, and SDK 0.5.6 release.

Verification

• npm run typecheck
• npm test: 347 passed.
• npm run build