v0.4.2

What's Changed

Retrieval Quality

• Power-law FTS boost: replace linear BM25-normalized boost with power-law scaling, concentrating boost on top FTS hits while staying grounded in actual BM25 relevance scores
• Tuned parameters via grid search (FTS_BOOST_MAX=0.12, FTS_GAMMA=2.0) — R@1: 45.5%, R@5: 78.0%, MRR: 59.3%, nDCG@5: 57.4%
• FTS params overridable via env vars in bench builds for parameter sweeps

Latency

• Batch chunk-to-item lookups (~30-60ms savings at 1,000 items)
• Raise brute-force vector search threshold to 5,000 rows for better accuracy on small tables
• Combined decay query: merge access + validation count lookups into single SQLite query