- Add v3.16.4 release notes in zh/en/ja.
- Add a trilingual FAQ explaining why custom models don't show in the Codex desktop model picker (upstream Codex Desktop login-identity gating, not a cc-switch bug) and the keep-official-login mitigation; cross-linked both ways with the official-auth preservation guide.
- Align the CHANGELOG 3.16.4 release date to 2026-06-27.
Jason