Add memory store integration tests

[Viperdk2020]

Summary

• add integration tests for memory store CRUD, import/export, and stats
• exercise recall and redaction APIs across JSONL and SQLite backends
• include tempfile dev dependency for test setup

Testing

• cargo test -p codex-memory (fails: not yet implemented at memory/src/store/jsonl.rs:7:9)

---

https://chatgpt.com/codex/tasks/task_e_68b510adf2148329ac7cbe453bfb8f63

[github-actions]

Thank you for your submission, we really appreciate it. Like many open-source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution. You can sign the CLA by just posting a Pull Request Comment same as the below format.

---

I have read the CLA Document and I hereby sign the CLA

---

_{You can retrigger this bot by commenting recheck in this Pull Request. Posted by the CLA Assistant Lite bot.}