Add typed Stage 5 promotion results

[anth-volk]

Fixes #1026

Summary

• Add typed Stage 5 promotion result dataclasses for HF, GCS, release manifest, version manifest, completion marker, cleanup, and full promotion outcomes.
• Add a compatibility wrapper that calls the existing transaction engine first, then converts the returned dictionary into FullPromotionResult.
• Preserve and extend transaction coverage for fresh promotion, already-finalized promotion, cleanup failure, skipped cleanup, and failure-before-write behavior.

Tests

• ruff check policyengine_us_data/release_promotion policyengine_us_data/utils/release_promotion.py tests/unit/release_promotion
• uv run --no-sync pytest tests/unit/release_promotion/test_results.py
• uv run --no-sync --with huggingface-hub --with google-cloud-storage --with google-auth --with httpx --with tenacity --with pytest --with pytest-dependency python -m pytest tests/unit/utils/test_data_upload.py tests/unit/release_promotion
• uv run --no-sync pytest tests/unit/test_stage_contracts.py tests/unit/release_promotion
• uv run --no-sync --with pyyaml python scripts/run_quality_guards.py
• uv run --no-sync --with pyyaml --with pytest pytest tests/unit/test_pipeline_docs_extractor.py tests/unit/test_pipeline_doc_guards.py
• uv run --no-sync --with pyyaml python scripts/extract_pipeline_docs.py --json /private/tmp/usdata-pipeline-docs-pr53/pipeline_map.json --api-json /private/tmp/usdata-pipeline-docs-pr53/pipeline_api.json --markdown /private/tmp/usdata-pipeline-docs-pr53/pipeline-map.md
• make lint