feat: UI translation adoption to Japanese and other languages

What version of the VS Code extension are you using?

0.4.0

Which IDE are you using?

Cursor 1.5.7

What platform is your computer?

Microsoft Windows NT 10.0.26100.0 x64

What steps can reproduce the bug?

Current Codex IDE is only adopted to English. Extend it to Japanese, and other languages, too.
Still, you can let AI agents read AGENTS.md and let it follow instructions and answers in Japanese.

<img width="562" height="1098" alt="Image" src="https://github.com/user-attachments/assets/47d1a7bc-47ab-4196-88b5-6f3990db1fb0" />

What is the expected behavior?

_No response_

What do you see instead?

_No response_

Additional information

_No response_