- Create ReproducibilityReport dataclass with all metadata fields
- Implement generate_reproducibility_report function
- Extract parameters from PipelineConfig (scoring weights, data versions)
- Capture software environment (Python, polars, duckdb versions)
- Build filtering steps from ProvenanceTracker
- Compute tier statistics from tiered DataFrame
- Support optional validation metrics
- to_json: write as indented JSON for machine-readable format
- to_markdown: write with tables and headers for human-readable format
- 7 tests covering all report fields, formats, and edge cases
