feat: add search filter bar for extension custom search

- Add SearchFilter struct in Go backend and Dart
- Add filters array to SearchBehaviorConfig manifest
- Add selectedSearchFilter state to TrackProvider
- Add filter bar UI with FilterChips below search bar
- Filter bar only shows when search results exist or loading
- Preserve selectedSearchFilter during customSearch loading
- Pass filter option to extension customSearch

lib/providers/extension_provider.dart

@@ -146,6 +146,26 @@ class Extension {
   bool get hasBrowseCategories => capabilities['browseCategories'] == true;
 }
 
+class SearchFilter {
+  final String id;
+  final String? label;
+  final String? icon;
+
+  const SearchFilter({
+    required this.id,
+    this.label,
+    this.icon,
+  });
+
+  factory SearchFilter.fromJson(Map<String, dynamic> json) {
+    return SearchFilter(
+      id: json['id'] as String? ?? '',
+      label: json['label'] as String?,
+      icon: json['icon'] as String?,
+    );
+  }
+}
+
 class SearchBehavior {
   final bool enabled;
   final String? placeholder;
@@ -154,6 +174,7 @@ class SearchBehavior {
   final String? thumbnailRatio; // "square" (1:1), "wide" (16:9), "portrait" (2:3)
   final int? thumbnailWidth;
   final int? thumbnailHeight;
+  final List<SearchFilter> filters; // Available search filters (e.g., track, album, artist, playlist)
 
   const SearchBehavior({
     required this.enabled,
@@ -163,6 +184,7 @@ class SearchBehavior {
     this.thumbnailRatio,
     this.thumbnailWidth,
     this.thumbnailHeight,
+    this.filters = const [],
   });
 
   factory SearchBehavior.fromJson(Map<String, dynamic> json) {
@@ -174,6 +196,9 @@ class SearchBehavior {
       thumbnailRatio: json['thumbnailRatio'] as String?,
       thumbnailWidth: json['thumbnailWidth'] as int?,
       thumbnailHeight: json['thumbnailHeight'] as int?,
+      filters: (json['filters'] as List<dynamic>?)
+          ?.map((f) => SearchFilter.fromJson(f as Map<String, dynamic>))
+          .toList() ?? [],
     );
   }
 

lib/providers/track_provider.dart

@@ -25,6 +25,7 @@ class TrackState {
   final bool hasSearchText; // For back button handling
   final bool isShowingRecentAccess; // For recent access mode
   final String? searchExtensionId; // Extension ID used for current search results
+  final String? selectedSearchFilter; // Currently selected search filter (e.g., "track", "album", "artist", "playlist")
 
   const TrackState({
     this.tracks = const [],
@@ -44,6 +45,7 @@ class TrackState {
     this.hasSearchText = false,
     this.isShowingRecentAccess = false,
     this.searchExtensionId,
+    this.selectedSearchFilter,
   });
 
   bool get hasContent => tracks.isNotEmpty || artistAlbums != null || (searchArtists != null && searchArtists!.isNotEmpty);
@@ -66,6 +68,8 @@ class TrackState {
     bool? hasSearchText,
     bool? isShowingRecentAccess,
     String? searchExtensionId,
+    String? selectedSearchFilter,
+    bool clearSelectedSearchFilter = false,
   }) {
     return TrackState(
       tracks: tracks ?? this.tracks,
@@ -85,6 +89,7 @@ class TrackState {
       hasSearchText: hasSearchText ?? this.hasSearchText,
       isShowingRecentAccess: isShowingRecentAccess ?? this.isShowingRecentAccess,
       searchExtensionId: searchExtensionId,
+      selectedSearchFilter: clearSelectedSearchFilter ? null : (selectedSearchFilter ?? this.selectedSearchFilter),
     );
   }
 }
@@ -391,7 +396,11 @@ class TrackNotifier extends Notifier<TrackState> {
   Future<void> customSearch(String extensionId, String query, {Map<String, dynamic>? options}) async {
     final requestId = ++_currentRequestId;
 
-    state = TrackState(isLoading: true, hasSearchText: state.hasSearchText);
+    state = TrackState(
+      isLoading: true,
+      hasSearchText: state.hasSearchText,
+      selectedSearchFilter: state.selectedSearchFilter, // Preserve filter during loading
+    );
 
     try {
       _log.i('Custom search started: extension=$extensionId, query="$query"');
@@ -423,6 +432,7 @@ class TrackNotifier extends Notifier<TrackState> {
         isLoading: false,
         hasSearchText: state.hasSearchText,
         searchExtensionId: extensionId, // Store which extension was used
+        selectedSearchFilter: state.selectedSearchFilter, // Preserve selected filter
       );
     } catch (e, stackTrace) {
       if (!_isRequestValid(requestId)) return;
@@ -474,6 +484,15 @@ class TrackNotifier extends Notifier<TrackState> {
     state = const TrackState();
   }
 
+  /// Set selected search filter for extension search
+  void setSearchFilter(String? filter) {
+    if (state.selectedSearchFilter == filter) return;
+    state = state.copyWith(
+      selectedSearchFilter: filter,
+      clearSelectedSearchFilter: filter == null,
+    );
+  }
+
   /// Set search text state for back button handling
   void setSearchText(bool hasText) {
     if (state.hasSearchText == hasText) {