Memory export/import support

[theantichris]

Summary

Support exporting and importing memory data, similar to conversation export (#203) and import (#204).

Motivation

Memory data (facts, summaries, associations) represents accumulated knowledge that users may want to:

• Back up before system changes or model upgrades
• Transfer between machines or ghost installations
• Share curated memory sets (e.g., project-specific knowledge)
• Reset by exporting, clearing, and selectively re-importing

Scope

• ghost memory export — export memory data to a portable format (JSON or similar)
• ghost memory import — import memory data from an exported file
• Handle merge semantics when importing into an existing memory store (duplicates, conflicts)

Related Issues

• Export conversations #203 — Conversation export
• Import conversations #204 — Conversation import
• Add memory storage engine #236 — Memory storage engine
• Integrate memory system into Ghost #239 — Integrate memory system

Notes

This is a future enhancement — no milestone assigned yet. The storage engine (#236) and integration (#239) should be implemented first to establish the memory data format.