Phase 4 of RFC #308: Stateful Sense refactor.
- CLAUDE.md: updated diagram, tables, examples (no more Signal)
- Cleaned stale Signal Bus / DrizzleDB / _signals / retention refs
across READMEs, .cursor rules, copilot instructions, .knowledge
- Removed drizzle-orm from core package.json (no longer used)
- Updated pnpm-lock.yaml
Refs #308