feat: LLM curator for named groups, haiku display, and docs overhaul
Replace per-cluster labeling with LLM-curated named groups:
- Claude Haiku 4.5 curates co-occurrence clusters into max 5 named
groups every 5 min with topic history for continuity
- Backend Group struct with case-insensitive entity matching
- POST /groups endpoint replaces /cluster-labels
- Frontend renders group pills, entity pips, and attributed haiku
- Relative trend arrows (percentile-based, not absolute thresholds)
- Fix: stats key rename crash loop (topics→groups in bridge.py)
- Fix: haiku container styling (Safari footer bleed, height collapse)
- Docs: rewrite architecture, add curator doc, update CLAUDE.md
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>