Switch from external Gemini API (3072 dims, $0.15/1M tokens) to local
Ollama mxbai-embed-large (1024 dims, free) for cost savings and HNSW
index support.
Changes:
- Updated embeddings.ts: model 'mxbai-embed-large', API URL fixed
- Updated migration 015: vector(1024) with HNSW index
- Regenerated 268 tool_docs embeddings with new model
Benefits:
- Free embeddings (no API costs)
- HNSW index enabled (1024 < 2000 dim limit)
- Fast similarity search (O(log n) vs O(n))
- No external API dependency
Trade-offs:
- 5% quality loss (MTEB 64.68 vs ~70 Gemini)
- Uses local compute (1.2GB RAM, <1s per embedding)
Task: CF-251
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
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