Implement JSONL memory store with path-aware persistence

[Viperdk2020]

Summary

• implement JSONL-backed MemoryStore with file persistence
• wire factory to pass repo/global paths to JsonlMemoryStore
• add compact helper to clean JSONL files for CLI

Testing

• just fmt
• just fix -p codex-memory
• cargo test -p codex-memory

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https://chatgpt.com/codex/tasks/task_e_68b5109d31488329a632b1f9e662700d

[github-actions]

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