feat(a2a): support detached tasks with bounded wait and durable replies

[410979729]

Summary

Support a2a_call(wait=false) using the A2A configuration.returnImmediately path, plus a2a_get_task and a2a_wait. Blocking calls retain their default behavior. Detached local and profile-backed work remains owned until completion rather than failing solely because a watchdog age threshold passes.

Keep terminal rejection/failure explanations queryable; clean up failed finalizer/thread starts; share a monotonic local wait budget across card discovery and task lookup; persist retrieved replies once by context/task/role rather than a short history tail. Include lazy tool metadata and documentation.

Related work

Related to #91688, #63946 and #55805. The existing open implementations were compared rather than treated as merged replacements. This candidate also covers bounded local waiting, profile-backed detached execution, terminal-error persistence and durable reply deduplication.

Verification

• 19 detached-task tests passed, including a real loopback HTTP submit → working → completed round trip and concurrency/error cases.
• 115 existing A2A tests, 1 schema-registration test and 4 focused lazy-discovery tests passed in separate native-Windows subprocesses.
• One unchanged POSIX fake-hermes profile fixture cannot execute on native Windows and fails identically on the base; excluded by its exact node name (test_forward_to_profile_first_contact_creates_then_resumes_fake_hermes).
• Focused lint and diff checks passed. Independent final static review found no remaining blocker within this scope.
• No claim of a whole-repository green suite or completed upstream CI.

Behavior remains in the existing adapter lifecycle, protocol persistence and outbound client-tool modules, with matching tests and plugin metadata; no core tool or separate infrastructure is introduced.

[alt-glitch]

This was generated by AI during triage.

Related: #91688 and #94880 are earlier open PRs for the same non-blocking A2A task goal (#91687), and #79721 covers late-finishing task results. This PR is a broader superset (detached wait=false, a2a_get_task/a2a_wait, durable reply dedup); flagging the cluster so a maintainer can choose or consolidate.