feat(google-adk): add released-runner TRACE adapter

[siiddhantt]

Summary

• add a first-party Google ADK BasePlugin adapter that emits TRACE v0.2 records from callback-visible evidence
• retain only invocation, model, available tool identity, and lifecycle outcomes; exclude prompts, arguments, results, responses, exception text, and raw function-call IDs
• exercise the released Google ADK 2.7.1 InMemoryRunner in CI and add the framework to the generated index and marketplace catalog

Evidence boundary

The adapter starts a run as incomplete and only reports success after root-agent completion plus after_run. It keeps terminal runner errors distinct, isolates concurrent invocations, fingerprints function-call IDs before retention, and refuses ambiguous model identity. Tool recovery and plugin short-circuit behavior are recorded as callback observations rather than claims that a function body ran.

Bare Google ADK does not enforce a TRACE policy, so enforcement_mode defaults to declared and appraisal.status remains none. agentrust-trace-tests 0.5.0 predates declared; the Level 0 conformance fixture uses advisory only for the documented path where an external layer actually evaluated the policy.

Verification

• 27 framework-free evidence and refusal tests
• 37 tests against google-adk 2.7.1, agentrust-trace 0.9.0, and agentrust-trace-tests 0.5.0 in clean Python 3.11, 3.12, and 3.13 environments
• repository Nox google_adk_adapter session passed on Python 3.12
• 16 repository validation tests passed; 17 integrations validated with zero failures
• Ruff, mypy, Bandit, generated-index, generated-catalog, YAML, JSON, and diff checks passed

Relates to #96

[imran-siddique]

Reviewed the adapter evidence boundary, payload exclusions, lifecycle handling, test coverage, and pinned CI dependencies. The implementation is fail-closed on ambiguous identity and keeps observed facts distinct from enforcement claims.