feat: surface duration gate summary markers

[hyeokjun32]

Summary

• add Validated Duration Traceability markers to the Runtime Intelligence artifact gate summary
• document the Lab-owned duration handoff/source/scope labels in CI and portfolio docs
• extend artifact gate tests so the generated summary and docs stay aligned

Tests

• poetry run python -m pytest -q tests/test_runtime_intelligence_artifact_gate.py -p no:cacheprovider
• poetry run python -m pytest -q tests/test_runtime_intelligence_artifact_gate.py tests/test_runtime_intelligence_ci_template.py tests/test_runtime_intelligence_smoke_script.py -p no:cacheprovider
• poetry run python -m pytest -q -p no:cacheprovider
• git diff --check
• bash scripts/smoke_runtime_intelligence_chain.sh --output-dir /private/tmp/inferedgelab_duration_gate_summary_20260601