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/session/SessionDialogs.tsx

@@ -491,7 +491,7 @@ export const SessionDialogs: React.FC = () => {
                         {targetWorktree ? formatPathForDisplay(targetWorktree.path, homeDirectory) : 'Worktree path unavailable.'}
                     </p>
                     {hasDirtyWorktrees && (
-                        <p className="typography-micro text-warning">Uncommitted changes will be discarded.</p>
+                        <p className="typography-micro text-status-warning">Uncommitted changes will be discarded.</p>
                     )}
 
                 </div>