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/lib/i18n/messages/ko.settings.ts

@@ -28,6 +28,10 @@ export const settingsDict = {
   'settings.view.actions.closeSettingsWithShortcut': '설정 닫기 ({shortcut}+,)',
   'settings.view.actions.back': '뒤로',
   'settings.view.actions.resizeNavigation': '설정 내비게이션 크기 조정',
+  'settings.view.search.placeholder': '설정 검색',
+  'settings.view.search.aria': '설정 검색',
+  'settings.view.search.clear': '설정 검색 지우기',
+  'settings.view.search.noResults': '일치하는 설정이 없습니다',
   'settings.page.projects.title': '프로젝트',
   'settings.page.remoteInstances.title': '원격 인스턴스',
   'settings.page.providers.title': '프로바이더',