feat: surface runtime replay duration source

[hyeokjun32]

Summary

• surface duration_source / duration_scope_label in the Runtime replay duration scope row
• preserve the traceability fields in the committed Runtime Intelligence fixture
• harden artifact and CI gates for the duration source/scope markers
• update docs to describe the Lab-owned replay duration traceability row

Tests

• poetry run python3 -m pytest -q tests/test_report_generators.py tests/test_runtime_intelligence_evidence_chain_smoke.py tests/test_runtime_intelligence_smoke_script.py tests/test_runtime_intelligence_artifact_gate.py tests/test_runtime_intelligence_ci_template.py -p no:cacheprovider
• git diff --check
• bash scripts/smoke_runtime_intelligence_chain.sh --output-dir /private/tmp/inferedgelab_duration_source_context_smoke_20260531_b
• poetry run inferedgelab portfolio-demo-check
• poetry run python3 -m pytest -q