Add faceting and metadata support to ColBERT

[jakemannix]

Add faceting and metadata support to ColBERT

- Added metadata support to Collection class with JSONL loading/saving
- Implemented faceted search in Searcher with filtering capabilities
- Added supporting methods for facet computation and filtering
- Created comprehensive tests for collection metadata and faceting
- Added pyproject.toml for better package management

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>

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    Add faceting benchmarks and test infrastructure

- Added script to generate synthetic datasets for faceting benchmarks
- Created pytest fixture for loading benchmark data with --benchmark-data-dir option
- Implemented test suite for metadata filtering and faceted search
- Added documentation on using metadata and faceting features
- Configured directory structure for storing benchmark test data

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>

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