feat(13-02): add library filter dropdown and wire all views to respect active filter

- Add selectedLibraryId state + ByLibrary conditional calls to library-store
- Add library filter pass-through methods to library-controller
- Create library-filter dropdown component in top bar
- Wire genre-details, cover-grid, artists-view, genres-view to use ByLibrary queries
- Update album-selection helper to respect library filter
- Regenerate Wails bindings for new ByLibrary methods
- Search remains client-side (automatically filtered by loaded data)
- Playlists remain unfiltered (use separate playlist store)

frontend/src/components/artists-view/artists-view.ts

@@ -13,6 +13,8 @@ import { grid } from '@lit-labs/virtualizer/layouts/grid.js';
 import {
     GetAlbumsByArtist,
     GetAlbumTracks,
+    GetAlbumsByArtistByLibrary,
+    GetAlbumTracksByLibrary,
 } from '@go/library/Library';
 import { library } from '@go/models';
 import { LibraryController } from '@store/controllers/library-controller';
@@ -927,20 +929,31 @@ export class ArtistsView
     /**
      * Fetches all file paths for an artist by
      * loading their albums, then each album's
-     * tracks.
+     * tracks.  Respects the active library filter.
      */
     private async getArtistFilePaths(
         artist: library.Artist,
     ): Promise<string[]> {
         try {
-            const albums =
-                await GetAlbumsByArtist(artist.ID);
+            const libId =
+                this.libraryCtrl.selectedLibraryId;
+
+            const albums = libId !== null
+                ? await GetAlbumsByArtistByLibrary(
+                      artist.ID,
+                      libId,
+                  )
+                : await GetAlbumsByArtist(artist.ID);
 
             const allPaths: string[] = [];
 
             for (const album of albums) {
-                const tracks =
-                    await GetAlbumTracks(album.ID);
+                const tracks = libId !== null
+                    ? await GetAlbumTracksByLibrary(
+                          album.ID,
+                          libId,
+                      )
+                    : await GetAlbumTracks(album.ID);
 
                 for (const t of tracks) {
                     allPaths.push(t.FilePath);

frontend/src/components/cover-grid/album-selection.ts

@@ -1,4 +1,8 @@
-import { GetAlbumTracks } from '@go/library/Library';
+import {
+    GetAlbumTracks,
+    GetAlbumTracksByLibrary,
+} from '@go/library/Library';
+import { libraryStore } from '@store/library-store';
 import type { library } from '@go/models';
 import type { CoverArtUrls } from '@components/track-details/track-details.js';
 
@@ -43,6 +47,21 @@ export class AlbumSelectionManager {
         this.albumFilePathCache.clear();
     }
 
+    /**
+     * Fetch album tracks respecting the active
+     * library filter.
+     */
+    private fetchAlbumTracks(
+        albumId: number,
+    ): Promise<library.Track[]> {
+        const libId =
+            libraryStore.getSelectedLibraryId();
+
+        return libId !== null
+            ? GetAlbumTracksByLibrary(albumId, libId)
+            : GetAlbumTracks(albumId);
+    }
+
     // ================================================================
     // Album selection helpers
     // ================================================================
@@ -134,9 +153,8 @@ export class AlbumSelectionManager {
         album: library.Album,
     ): Promise<string[]> {
         try {
-            const tracks = await GetAlbumTracks(
-                album.ID,
-            );
+            const tracks =
+                await this.fetchAlbumTracks(album.ID);
 
             return tracks.map((t) => t.FilePath);
         } catch (error) {
@@ -174,9 +192,10 @@ export class AlbumSelectionManager {
             if (!album) continue;
 
             try {
-                const tracks = await GetAlbumTracks(
-                    album.ID,
-                );
+                const tracks =
+                    await this.fetchAlbumTracks(
+                        album.ID,
+                    );
 
                 // Only store if still selected.
                 if (selectedAlbums.has(album.ID)) {

frontend/src/components/cover-grid/cover-grid.ts

@@ -11,7 +11,10 @@ import type {
     VisibilityChangedEvent,
 } from '@lit-labs/virtualizer';
 import { grid } from '@lit-labs/virtualizer/layouts/grid.js';
-import { GetAlbumTracks } from '@go/library/Library';
+import {
+    GetAlbumTracks,
+    GetAlbumTracksByLibrary,
+} from '@go/library/Library';
 import { library } from '@go/models';
 import { LibraryController } from '@store/controllers/library-controller';
 import { SearchController } from '@store/controllers/search-controller';
@@ -973,9 +976,15 @@ export class CoverGrid
         this.lastSelectedTrackIndex = null;
 
         try {
-            const tracks = await GetAlbumTracks(
-                album.ID,
-            );
+            const libId =
+                this.libraryCtrl.selectedLibraryId;
+
+            const tracks = libId !== null
+                ? await GetAlbumTracksByLibrary(
+                      album.ID,
+                      libId,
+                  )
+                : await GetAlbumTracks(album.ID);
 
             if (this.expandedAlbumId === album.ID) {
                 this.expandedTracks = tracks;

frontend/src/components/genre-details/genre-details.ts

@@ -5,9 +5,13 @@ import {
     state,
 } from 'lit/decorators.js';
 import { library } from '@go/models';
-import { GetTracksByGenre } from '@go/library/Library';
+import {
+    GetTracksByGenre,
+    GetTracksByGenreByLibrary,
+} from '@go/library/Library';
 import { EventsOn } from '@runtime/runtime';
 import { Events } from '../../events';
+import { libraryStore } from '@store/library-store';
 import '@awesome.me/webawesome/dist/components/icon/icon.js';
 import '@components/track-list/track-list.js';
 import { designTokens } from '../../styles/tokens.css';
@@ -176,9 +180,17 @@ export class GenreDetails extends LitElement {
         if (!this.genreName) return;
 
         try {
-            this.tracks = await GetTracksByGenre(
-                this.genreName,
-            );
+            const libId =
+                libraryStore.getSelectedLibraryId();
+
+            this.tracks = libId !== null
+                ? await GetTracksByGenreByLibrary(
+                      this.genreName,
+                      libId,
+                  )
+                : await GetTracksByGenre(
+                      this.genreName,
+                  );
         } catch (error) {
             console.error(
                 'Error loading genre tracks:',

frontend/src/components/genres-view/genres-view.ts

@@ -10,7 +10,10 @@ import type {
     VisibilityChangedEvent,
 } from '@lit-labs/virtualizer';
 import { grid } from '@lit-labs/virtualizer/layouts/grid.js';
-import { GetTracksByGenre } from '@go/library/Library';
+import {
+    GetTracksByGenre,
+    GetTracksByGenreByLibrary,
+} from '@go/library/Library';
 import type { library } from '@go/models';
 import { LibraryController } from '@store/controllers/library-controller';
 import { SearchController } from '@store/controllers/search-controller';
@@ -723,16 +726,25 @@ export class GenresView
     /**
      * Fetch file paths for a set of genre names by
      * querying the backend for each genre.
+     * Respects the active library filter.
      */
     private async getFilePathsForGenres(
         genreNames: Iterable<string>,
     ): Promise<string[]> {
         const seen = new Set<string>();
         const allPaths: string[] = [];
+        const libId =
+            this.libraryCtrl.selectedLibraryId;
 
         const promises = Array.from(
             genreNames,
-            (name) => GetTracksByGenre(name),
+            (name) =>
+                libId !== null
+                    ? GetTracksByGenreByLibrary(
+                          name,
+                          libId,
+                      )
+                    : GetTracksByGenre(name),
         );
 
         const results = await Promise.all(promises);

frontend/src/components/library-filter/library-filter.ts

@@ -0,0 +1,107 @@
+import { LitElement, html, css } from 'lit';
+import { customElement, state } from 'lit/decorators.js';
+import { LibraryController } from '@store/controllers/library-controller';
+import type { library } from '@go/models';
+import { designTokens } from '../../styles/tokens.css';
+
+/**
+ * Compact dropdown in the top bar for filtering all
+ * browse views to a specific library.  "All Libraries"
+ * (value = null) shows the unified merged view.
+ */
+@customElement('library-filter')
+export class LibraryFilter extends LitElement {
+    private libraryCtrl = new LibraryController(this);
+
+    @state()
+    private libraries: library.Info[] = [];
+
+    static override styles = [designTokens, css`
+        :host {
+            display: flex;
+            align-items: center;
+        }
+
+        select {
+            height: 32px;
+            padding: 0 8px;
+            border-radius: 6px;
+            border: 1px solid
+                var(--yj-border-subtle, #555);
+            background: var(--yj-bg-surface, #212529);
+            color: var(--yj-text-primary, #fff);
+            font-size: var(--yj-text-md);
+            font-family: inherit;
+            cursor: pointer;
+            outline: none;
+            min-width: 120px;
+            max-width: 200px;
+        }
+
+        select:focus {
+            border-color: var(--yj-accent, #ffd43b);
+        }
+
+        option {
+            background: var(--yj-bg-surface, #212529);
+            color: var(--yj-text-primary, #fff);
+        }
+    `];
+
+    override connectedCallback() {
+        super.connectedCallback();
+        this.loadLibraries();
+    }
+
+    private async loadLibraries() {
+        try {
+            this.libraries =
+                await this.libraryCtrl.getLibraries();
+        } catch (error) {
+            console.error(
+                'Error loading libraries:',
+                error,
+            );
+        }
+    }
+
+    private handleChange = (e: Event) => {
+        const select = e.target as HTMLSelectElement;
+        const value = select.value;
+        const id = value === ''
+            ? null
+            : Number(value);
+
+        this.libraryCtrl.setSelectedLibrary(id);
+    };
+
+    override render() {
+        const selected =
+            this.libraryCtrl.selectedLibraryId;
+        const selectValue =
+            selected === null ? '' : String(selected);
+
+        return html`
+            <select
+                .value=${selectValue}
+                @change=${this.handleChange}
+                aria-label="Library filter"
+            >
+                <option value="">All Libraries</option>
+                ${this.libraries.map(
+                    (lib) => html`
+                        <option value=${lib.id}>
+                            ${lib.name}
+                        </option>
+                    `,
+                )}
+            </select>
+        `;
+    }
+}
+
+declare global {
+    interface HTMLElementTagNameMap {
+        'library-filter': LibraryFilter;
+    }
+}