feat: add Runtime timeout observation evidence

[hyeokjun32]

Summary

• Added --timeout-ms as a Runtime-side latency threshold observation option.
• Records timeout_policy, timeout_budget_ms, timeout_observed, and runtime_timeout_observed classification in additive operation evidence blocks.
• Updated Runtime docs and smoke/schema tests while preserving Lab-compatible result fields.

Validation

• bash scripts/smoke_default.sh
• python3 tests/test_manifest_compare_identity.py
• python3 tests/test_agent_runtime_result_contract.py
• python3 -m unittest discover -s tests -p 'test_*.py'
• git diff --check

Notes

• This is observation evidence for downstream Orchestrator/Lab/AIGuard reporting.
• It does not implement production request cancellation or a worker daemon.