Update docs with missing modules, hybrid search, and benchmark details

[rendro]

Summary

• CLAUDE.md: Add 4 missing modules to Core Components (document.rs, item.rs, error.rs, retry.rs), fix similarity boosting description to match actual code (0.875x cross-project penalty, not 1.15x/0.95x), document hybrid FTS/BM25 search, add SQLite indexes to schema
• README.md: Add hybrid search as a key feature, fix project scoping description to reflect penalty-based (not boost-based) behavior
• BENCHMARKS.md: Add nDCG@5 metric, per-category Recall@5 and MRR breakdowns, expanded temporal correctness table, and p50/p95/p99 latency tables sourced from latest sediment-bench run

Test plan

• Verify all markdown renders correctly on GitHub
• Cross-check benchmark numbers against sediment-bench/results/report.md
• Confirm similarity boosting values match lib.rs::boost_similarity()