Add runtime operation summary evidence

[hyeokjun32]

Summary

• add additive runtime_operation_summary handoff block to Runtime result JSON
• add health_reason and runtime_operation_summary_recorded lifecycle event for downstream Lab/Orchestrator/AIGuard interpretation
• extend Runtime contract tests, smoke assertions, timeout fixture, and docs

Tests

• bash scripts/smoke_default.sh
• python3 tests/test_agent_runtime_result_contract.py
• python3 tests/test_lab_result_schema.py
• python3 tests/test_manifest_compare_identity.py
• python3 -m unittest discover tests
• python3 -m json.tool tests/fixtures/runtime_timeout_observed_result.json
• git diff --check