fix: restore reliable update flow across sidebar and mobile

Show Update button in sidebar only when an update is available
Support update button on mobile sidebar and remove duplicate mobile Settings entry
Force desktop Tauri recheck and preflight before download to avoid missing pending updates

packages/ui/src/components/views/SettingsView.tsx

@@ -51,7 +51,6 @@ import { UsagePage } from '@/components/sections/usage/UsagePage';
 import { GitPage } from '@/components/sections/git-identities/GitPage';
 import type { OpenChamberSection } from '@/components/sections/openchamber/types';
 import { OpenChamberPage } from '@/components/sections/openchamber/OpenChamberPage';
-import { AboutSettings } from '@/components/sections/openchamber/AboutSettings';
 import { McpIcon } from '@/components/icons/McpIcon';
 import { useDeviceInfo } from '@/lib/device';
 import { isDesktopShell, isVSCodeRuntime, isWebRuntime } from '@/lib/desktop';
@@ -568,11 +567,6 @@ export const SettingsView: React.FC<SettingsViewProps> = ({ onClose, forceMobile
               </Tooltip>
             )}
 
-            {isMobile && runtimeCtx.isWeb && (
-              <div className="px-1.5 pt-2">
-                <AboutSettings />
-              </div>
-            )}
           </div>
         </div>
       </div>