docs(adr): ADR-036 CleoOS Database Topology + Lifecycle

T300 — Wave 0 of T299 v2026.4.11 epic.

Documents the full 4-DB × 2-tier CleoOS database topology as the
architectural anchor for v2026.4.11's nine topology+lifecycle tasks.

- Project tier: tasks.db + brain.db + signaldock.db + config.json + project-info.json
- Global tier (XDG via env-paths): nexus.db + global signaldock.db + machine-key
- Walk-up first-hit scaffolding rule (never auto-create nested .cleo/)
- VACUUM INTO backup mechanism with 10-snapshot rotation per tier
- Cross-machine portability direction (deferred to T311)
- Signaldock dual-scope direction (deferred to T310)

Closes the work started in ADR-013 §9. Synced into architecture_decisions DB.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: kryptobaseddev