feat: complete Milestone 5 — full-text search, RRF fusion, and creator search
- M5p1: BM25 text indexing via Tantivy with background syncer (0.26ms @ 10K docs)
- M5p2: RRF fusion layer combining BM25 + ANN scores (46µs @ 1K candidates)
- M5p3: unified Search query API (8-stage pipeline, BM25 + vector + ranking)
- M5p4: creator text + vector indexing and creator search executor (< 20ms @ 200 creators)
- Refactor db/mod.rs into focused sub-modules (creators, items, sessions, signals, etc.)
- Decompose monolithic files into directory modules (query/executor, ranking/diversity, etc.)
- Split brute.rs → brute/mod.rs + brute/tests.rs; extract search executor helpers
- Add benches: fusion, search, session, text_index
- Add M5 UAT test suites (m5_uat, m5_search, m5p4_creator_search, text_index)
- Update blog posts, roadmap, content strategy, and M5 planning docs
- Add tmp/ and .claude/worktrees/ to .gitignore
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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