Add i18n internationalization support

[guixiao2026]

Summary

Add a JSON-based internationalization (i18n) system to WinUtil, allowing the UI to be translated into any language by simply adding a locale JSON file.

What changed

File	Change
Compile.ps1	Exclude locales/ from preprocessing; embed locale JSON with explicit UTF-8 reading; output compiled script with UTF-8 BOM to preserve non-ASCII characters
functions/private/Set-WinUtilLanguage.ps1	New file — three functions: Set-WinUtilLanguage (config overlay with English fallback), Set-WinUtilLanguageUI (XAML element updates), Get-WinUtilAvailableLanguages (locale discovery)
locales/en.json	English reference template with UI string keys
locales/zh-TW.json	Complete Traditional Chinese translation — UI strings, categories, tweak/feature descriptions, and application tooltips
scripts/main.ps1	Language button initialization, menu population, language switch handler with panel rebuild, handler re-binding, and checkbox state preservation
xaml/inputXML.xaml	Language button (globe icon) and popup menu in the toolbar

How it works

1. Locale files in locales/*.json are embedded during compilation
2. A globe button in the toolbar opens a language picker
3. On language switch, original English configs are saved (first call only), restored, then translated values are overlaid
4. UI panels are rebuilt with translated content; click handlers and checkbox states are preserved
5. Missing translation keys fall back to English automatically

How to add a new language

1. Copy locales/en.json to locales/{locale-code}.json (e.g., ja.json)
2. Fill in _metadata.name with the display name (e.g., "日本語")
3. Translate the ui, categories, and description fields
4. Run .\Compile.ps1 — the new language appears automatically in the menu

Design decisions

• No runtime file I/O — all locales are embedded at compile time, matching WinUtil's single-file distribution model
• Config overlay approach — original configs are deep-cloned and restored before each switch, ensuring clean state
• Explicit UTF-8 handling — [System.IO.File]::ReadAllText() with UTF-8 encoding avoids corruption on non-English Windows systems where default encoding may be ANSI/Big5
• Minimal footprint — only 6 files changed, no new dependencies, zero impact when no language switch is performed

Test plan

• Compile with .\Compile.ps1 and verify syntax validation passes
• Launch winutil, switch to 繁體中文, verify all UI elements translate
• Switch back to English, verify full restoration
• Switch languages multiple times, verify no handler duplication (buttons don't fire multiple times)
• Verify checkbox states are preserved across language switches
• Verify Button-type controls (Ultimate Performance, Region, etc.) remain functional after switch
• Verify package manager radio button preference persists after switch
• Verify winutil.ps1 is not included in the commit

[GabiNun]

This approach works well, but with each language we add to winutil via this PR, the winutil.ps1 file increases by about 100 KB. Adding 12 more languages would bring it close to 2 MB.

@ChrisTitusTech
@guixiao2026

[Kingproone]

This approach works well, but with each language we add to winutil via this PR, the winutil.ps1 file increases by about 100 KB. Adding 12 more languages would bring it close to 2 MB.

what if during build, every language gets its own .ps1 build, tagged with the built language?
with this the user could manually choose which language they would like to use (english being the default), for example:

irm "https://christitus.com/win-zh" | iex

irm "https://christitus.com/windev-zh" | iex

one step further: when running the stable branch, it could check for the current user locale, and download the corresponding ps1 file.

[GabiNun]

This approach works well, but with each language we add to winutil via this PR, the winutil.ps1 file increases by about 100 KB. Adding 12 more languages would bring it close to 2 MB.

what if during build, every language gets its own .ps1 build, tagged with the built language? with this the user could manually choose which language they would like to use (english being the default), for example:

irm "https://christitus.com/win-zh" | iex

irm "https://christitus.com/windev-zh" | iex

one step further: when running the stable branch, it could check for the current user locale, and download the corresponding ps1 file.

ye im pretty sure thats what chris wants

[guixiao2026]

Let me think about it.