Fixed inverted eviction scoring formula in UnifiedCache that was causing
metadata (cheap to rebuild) to be retained while HNSW vectors (expensive,
frequently accessed) were evicted. This was causing OOM crashes during
large Excel imports with relationship extraction.
Changes:
- evictLowestValue(): Changed accessScore / rebuildCost to accessScore * rebuildCost
- evictForSize(): Changed accessScore / rebuildCost to accessScore * rebuildCost
- evictType(): Changed accessScore / rebuildCost to accessScore * rebuildCost
With the corrected formula, items with higher access counts AND higher
rebuild costs get higher scores and are protected from eviction.
Test coverage: Added comprehensive eviction scoring tests
Fixes: Type metadata hogging 99.7% of cache with only 3.7% access rate
