[i18n] Chinese UI improvements: language switcher + translation fixes

[yanba109-m4]

[i18n] Chinese UI improvements: language should be switchable in UI + translation fixes

Hi, thank you for the amazing work on ACE-Step 1.5! I'm using it daily for music production on my RTX 4070 Ti SUPER.

I'd like to report two i18n-related issues and share the fixes I've already made locally.

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Issue 1: UI Language selector is locked (not switchable at runtime)

In Settings → Service Configuration, the UI Language dropdown shows the current language but is not interactive — users cannot switch languages without editing start_gradio_ui.bat and restarting.

This is a poor experience for Chinese users who don't know how to edit bat files. Ideally, the language dropdown should work like a normal selector: pick a language → UI refreshes immediately.

Issue 2: zh.json translation quality issues

The current Chinese translation has several problems:

Key	Current zh.json	Problem	Suggested fix
generation.cot_metas_label	CoT メタデータ	Japanese text leaked into Chinese file	CoT 元数据
generation.cot_metas_info	LMを使用してCoTメタデータを生成...	Entire value is Japanese	使用 LM 生成 CoT 元数据
generation.*codes* (8 places)	代码	Means "programming code", confusing	编码 (audio codes)
service.offload_cpu_label	卸载到CPU	Sounds like "uninstall"	闲置时转移到 CPU
app.title	演练场	Uncommon translation for Playground	游乐场
help.getting_started	设置手风琴	Literal translation of "accordion"	设置面板

Also, the Generation Mode radio buttons (Simple / Custom / Remix / Repaint) remain in English even when zh is selected, because these values appear to be hardcoded rather than pulled from the i18n file.

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What I did locally (workaround)

1. Edited start_gradio_ui.bat: changed LANGUAGE=en → LANGUAGE=zh
2. Replaced zh.json with a corrected version fixing all issues listed above

This works, but gets overwritten on every update.

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Suggestions for next release

1. Make the UI Language dropdown interactive so users can switch languages without restarting
2. Fix the Japanese text that leaked into zh.json (copy-paste error from ja.json)
3. Pull Generation Mode labels from i18n instead of hardcoding English strings
4. Review zh.json — I'm happy to submit a corrected version as a PR if helpful

Thanks again for the great project! 🎵

Environment: Windows portable package, RTX 4070 Ti SUPER 16GB, v1.5

[ChuxiJ]

Issue 2 see: #790

[ChuxiJ]

Issue 1: https://deepwiki.com/search/gradio-ui_3d3bd7b1-c730-461a-b8f2-daf5772270fe?mode=fast