[M1-M5] Shared Hub memory lifecycle and retention controls

[ACFHarbinger]

Track the implemented local-first memory slice.

Implemented in commits 8903e88, a41cdf4, and 7b972fc:

• SQLite memory tiers with promotion, compaction, provenance, deletion, and stale marking.
• Short-term age-out and permanent stale-memory purge.
• CLI and Tauri access plus desktop Shared Hub review.
• Markdown export includes high-priority handoffs.

Roadmap: docs/moon/roadmaps/memory.md.

Remaining work: automated TTL scheduling, optional private-journal encryption, and the M6 end-to-end acceptance gate.

[ACFHarbinger]

Implemented and verified in commits 7b972fc and 14f43ab. Memory tiers, promotion/compaction, stale purge, age-out, provenance exposure, CLI/Tauri access, and Shared Hub review are covered. cargo test --workspace and npm run build pass.