docs: Add reconstruction specification for AI reproducibility

A compressed specification enabling AI reconstruction of the codebase,
capturing:
- Mathematical foundations (Bregman divergences, Lloyd's algorithm)
- All 8 divergence implementations with formulas
- Architecture and core traits
- 20+ algorithm variants
- Parameters, persistence, and testing requirements
- Key implementation details for correct behavior

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: derrickburns