feat(settings): add item search (#1592)

Adds item-level search inside Settings so users can find concrete settings like provider auth, agent mode, terminal font size, tunnel options, notification events, and similar controls instead of only filtering top-level pages.
Groups search results by Settings page and shows localized labels plus optional descriptions where useful.
Supports keyboard navigation with Arrow Up/Down, Enter, and Escape, matching the existing autocomplete interaction style.
Opens the correct Settings page or split-page draft state before scrolling to the matching control.
Highlights the matched setting with a subtle token-based background so users can see where they landed without an aggressive outline.
Adds explicit data-settings-item anchors across Settings pages and a centralized search registry with runtime/mobile availability guards.
Updates Settings UI skill guidance so future Settings changes keep search registry entries, anchors, localization, and availability guards in sync.

packages/ui/src/components/sections/magic-prompts/MagicPromptsPage.tsx

@@ -326,6 +326,7 @@ export const MagicPromptsPage: React.FC = () => {
             </div>
           </div>
           <Button
+            data-settings-item="magic-prompts.reset-overrides"
             variant="outline"
             size="sm"
             onClick={() => {
@@ -348,7 +349,11 @@ export const MagicPromptsPage: React.FC = () => {
           const resetting = resettingIds[block.id] === true;
 
           return (
-            <section key={block.id} className={index > 0 ? 'space-y-3 pt-5 border-t border-border' : 'space-y-3'}>
+            <section
+              key={block.id}
+              data-settings-item={isVisiblePromptId(block.id) ? 'magic-prompts.visible-prompt' : 'magic-prompts.instructions'}
+              className={index > 0 ? 'space-y-3 pt-5 border-t border-border' : 'space-y-3'}
+            >
               <div className="space-y-1">
                 <div className="flex flex-wrap items-center gap-2">
                   <h3 className="typography-ui-label text-foreground">{tUnsafe(block.titleKey)}</h3>