New zh/en/ja guide for the unified Codex session-history toggle: what opt-in migration (on enable) and ledger-based restore (on disable) actually do, why session data is never truly deleted (tag-only rewrite + automatic backups), and how to verify files on disk versus just being filed under another provider drawer. Includes a symptom reference table for the common "my sessions are gone" misunderstanding and on-disk verification commands for macOS/Linux/Windows.
Link the guide as the lead item in the "Usage Guides" section of the v3.16.3 release notes (zh/en/ja).
Jason
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