[Feature Request]: Add theme support (dark mode + VS Code theme import) in Desktop GUI

[lidao2026-Coding]

Is your feature request related to a problem?

Yes. The Desktop GUI only ships the default light theme — there is no dark theme and no way to customize the color scheme. For a coding tool used for long sessions, the lack of theme support is a significant usability gap (many developers work in dark mode).

Describe the solution you'd like

Add basic theme support for the Desktop app:

1. Ship at least a built-in Dark theme alongside the default.
2. Provide a theme entry point (Settings → Appearance) with an option like "Import VS Code theme (.json)" that loads a Theme+ColorTheme file (VS Code's colorTheme format) and maps its workbench/editor colors to the Desktop UI via CSS variables.
3. Follow system OS light/dark preference by default, with a manual override.

Since the Desktop frontend is React + CSS (see desktop/src/**), reusing the mature VS Code theme ecosystem (settings.json / .json color themes) dramatically lowers implementation cost — no need to design a theme system from scratch.

Describe alternatives you've considered

• Supporting only a fixed dark/light toggle (works, but users can't personalize).
• Building a custom theme format (more work, smaller ecosystem).

Additional context

• Platform: Windows 11.
• The VS Code theme format is JSON and widely documented; tools like theme.json from the VS Code marketplace can be imported directly.
• Version: DeepCode Desktop 0.1.0 (v2.0.0 runtime).

[Zongwei9888]

Thanks for raising this. Good news first: a dark theme is already there. It's been in the app since the Tauri rewrite and follows your OS setting automatically — if you switch Windows 11 to dark mode, DeepCode should follow. Worth a try, in case that covers what you needed.

What was genuinely missing is the ability to override the OS, and that's now in #161: Settings → Appearance → Theme, with Match system / Light / Dark.

VS Code theme import isn't done yet. Mapping an external theme format onto our tokens needs a bit more thought than the toggle did, so we've left it for a follow-up. Keeping this issue open for that part.