- Wire btree.scan() for BETWEEN, >, >=, <, <= conditions
- When a B-Tree index exists and WHERE clause is a range condition,
the executor now uses index range scan instead of full table scan
- Add 3 unit tests: BETWEEN, >, <=
- Update PLAN.md / PLAN_DONE.md
- PLAN_DONE.md: everything completed so far
- PLAN.md: only real remaining work (no Partitioning, no Kubernetes)
- Explicitly marks WebSocket auth, B-Tree range scans, JSON types as critical
dimgigov