fix: add Google runtime timings and ADK worker warmup

[creatornader]

Summary

• add operation timing output to the Google evidence runtime
• run A2A proof work asynchronously and reuse a warmed ADK Python decision worker
• prime the worker from /v1/runtime-state so the hosted demo does not present Python startup as decision latency

Verification

• pnpm --filter @atrib/integration typecheck
• pnpm --filter @atrib/integration test -- a2a-handoff google-evidence-runtime
• ATRIB_GOOGLE_ADK_PYTHON_WORKER=1 pnpm --filter @atrib/integration google-adk-python-decision-ledger-proof >/dev/null
• python3 -m py_compile packages/integration/examples/google-adk-python/google-adk-python-decision-ledger-proof.py
• git diff --check