feat: introduced a token-based theming system across the UI

* feat: added themes system

* feat: smart sidebar auto-hide for files/diff tabs + lower files sidebar threshold

* feat: added Checkbox component and update theming

- Add reusable Checkbox component for toggles across UI
- Replace several inputs with Checkbox in settings and commands panels
- Add DiffIcon and apply surface/border theming to key UI areas

* feat: Add convert-vscode-theme.cjs to convert VS Code themes to OpenChamber format

* refactor: remove unused permission logic from ChatInput

- Remove unused permission rules parsing logic from ChatInput
- Memoize renderTheme in DiffWorkerProvider to avoid unnecessary recalculations
- Remove forceOpaque helper in vscode theme adapter

* fix: guard VSCode theme loading in MarkdownRenderer

* feat: add custom user themes loading and reload

- Load user themes from ~/.config/openchamber/themes at runtime
- Expose /api/config/themes to fetch custom themes
- Allow theme reloading from Settings → Theme → Reload themes in the UI

packages/ui/src/components/chat/ChatErrorBoundary.tsx

@@ -60,7 +60,7 @@ export class ChatErrorBoundary extends React.Component<ChatErrorBoundaryProps, C
 
               {this.state.error && (
                 <details className="text-xs font-mono bg-muted p-3 rounded">
-                  <summary className="cursor-pointer hover:bg-muted/80">Error details</summary>
+                  <summary className="cursor-pointer hover:bg-interactive-hover/80">Error details</summary>
                   <pre className="mt-2 overflow-x-auto">
                     {this.state.error.toString()}
                   </pre>
@@ -85,4 +85,4 @@ export class ChatErrorBoundary extends React.Component<ChatErrorBoundaryProps, C
 
     return this.props.children;
   }
-}
+}