restore the code editor screen, drop the dead theme picker, unshadow AppRegistry

Three unrelated type errors that each pointed at something actually broken:

- Dashboard.CodeEditor was deleted in ab03b17 ("Projects") while the
  /code-editor route and the dock's Editor item kept pointing at it, so the
  route rendered undefined. Screen restored.

- Appearance.tsx imported 'themes', a workspace deleted in 0746844. Nothing
  reads settings.appearance.colorTheme and no theme CSS survives, so the picker
  was writing a value with no consumer. Removed it and the setting; colorMode
  stays, it is live.

- officerdev exported both a component and a type named AppRegistry, so
  `import { AppRegistry }` resolved to the type and <AppRegistry /> failed to
  typecheck. Renamed the Record type to AppRegistryMap.

Also declares "*.css" so side-effect stylesheet imports resolve.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/workspaces/state/src/useSettings.ts

@@ -68,7 +68,6 @@ export type UserSettings = {
   };
   appearance: {
     colorMode: 'light' | 'dark';
-    colorTheme: string;
   };
   languages: {
     spoken: string[];
@@ -105,7 +104,6 @@ export const DEFAULT_SETTINGS: UserSettings = {
   },
   appearance: {
     colorMode: 'light',
-    colorTheme: 'DuckPond',
   },
   languages: {
     spoken: ['en'],