feat: add recall-backed memories panel

[Viperdk2020]

Summary

• use recall engine for durable preamble
• add memories panel with CRUD support
• test panel rendering and preamble preview

Testing

• cargo test -p codex-memory
• cargo test -p codex-tui

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https://chatgpt.com/codex/tasks/task_e_68b510a6a0448329a2d5cf4fa55da9ac

[github-actions]

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