feat(library): genre sliders, artist links, and navigation utils

- music landing: diverse per-genre album sliders (online counts /
  offline wide-probe fallback) and home-screen library shortcuts
- add ArtistLinks component and shared navigation/genreDiversity utils
- player/playback-mode refinements across Rust and frontend

src/lib/stores/playbackMode.test.ts

@@ -9,26 +9,31 @@ vi.mock("@tauri-apps/api/core", () => ({
   invoke: (...args: unknown[]) => mockInvoke(...args),
 }));
 
-// Mock the sessions store
+// Mock the sessions store. `selectedSession` is read via svelte's `get()`, which
+// calls subscribe and synchronously receives the current value; tests set
+// `currentSelectedSession` to control what the store yields.
 const mockSelectSession = vi.fn();
+let currentSelectedSession: unknown = null;
 vi.mock("./sessions", () => ({
   sessions: {
     selectSession: (...args: unknown[]) => mockSelectSession(...args),
   },
   selectedSession: {
-    subscribe: vi.fn((callback: (value: null) => void) => {
-      callback(null);
+    subscribe: vi.fn((callback: (value: unknown) => void) => {
+      callback(currentSelectedSession);
       return () => {};
     }),
   },
 }));
 
 // Mock auth store
+const mockGetHandle = vi.fn(() => "repo-handle-1");
 vi.mock("./auth", () => ({
   auth: {
     getRepository: vi.fn(() => ({
       getPlaybackInfo: vi.fn().mockResolvedValue({ streamUrl: "http://test.com/stream" }),
       getImageUrl: vi.fn().mockReturnValue("http://test.com/image"),
+      getHandle: () => mockGetHandle(),
     })),
   },
 }));
@@ -36,6 +41,7 @@ vi.mock("./auth", () => ({
 describe("playbackMode store", () => {
   beforeEach(() => {
     vi.clearAllMocks();
+    currentSelectedSession = null;
   });
 
   afterEach(() => {
@@ -204,6 +210,90 @@ describe("playbackMode store", () => {
     });
   });
 
+  describe("transferToLocal", () => {
+    // 50,000,000 ticks = 5 seconds (10M ticks per second).
+    const REMOTE_POSITION_TICKS = 50_000_000;
+    const REMOTE_POSITION_SECONDS = 5;
+
+    function setRemoteSessionPlaying() {
+      currentSelectedSession = {
+        id: "session-123",
+        nowPlayingItem: { id: "item-abc", name: "Test Track", runTimeTicks: 1_800_000_000 },
+        playState: { positionTicks: REMOTE_POSITION_TICKS },
+      };
+    }
+
+    it("resumes local playback at the remote position, not from 0", async () => {
+      const { playbackMode } = await import("./playbackMode");
+
+      playbackMode.setMode("remote", "session-123");
+      setRemoteSessionPlaying();
+      mockInvoke.mockResolvedValue(undefined);
+
+      await playbackMode.transferToLocal();
+
+      // Bug 2 guard: the resume position must be passed to play_tracks so the
+      // backend seeks at load time. Restarting from 0 means startPosition is missing.
+      const playTracksCall = mockInvoke.mock.calls.find((c) => c[0] === "player_play_tracks");
+      expect(playTracksCall).toBeDefined();
+      expect(playTracksCall![1]).toMatchObject({
+        repositoryHandle: "repo-handle-1",
+        request: {
+          trackIds: ["item-abc"],
+          startIndex: 0,
+          startPosition: REMOTE_POSITION_SECONDS,
+        },
+      });
+    });
+
+    it("does not issue a separate player_seek (no start-at-0-then-jump race)", async () => {
+      const { playbackMode } = await import("./playbackMode");
+
+      playbackMode.setMode("remote", "session-123");
+      setRemoteSessionPlaying();
+      mockInvoke.mockResolvedValue(undefined);
+
+      await playbackMode.transferToLocal();
+
+      const seekCall = mockInvoke.mock.calls.find((c) => c[0] === "player_seek");
+      expect(seekCall).toBeUndefined();
+    });
+
+    it("tells Rust to stop the remote session with the current item and position", async () => {
+      const { playbackMode } = await import("./playbackMode");
+
+      playbackMode.setMode("remote", "session-123");
+      setRemoteSessionPlaying();
+      mockInvoke.mockResolvedValue(undefined);
+
+      await playbackMode.transferToLocal();
+
+      expect(mockInvoke).toHaveBeenCalledWith("playback_mode_transfer_to_local", {
+        currentItemId: "item-abc",
+        positionTicks: REMOTE_POSITION_TICKS,
+      });
+
+      const state = get(playbackMode);
+      expect(state.mode).toBe("local");
+      expect(state.remoteSessionId).toBeNull();
+      expect(state.isTransferring).toBe(false);
+    });
+
+    it("switches to local without playing media when remote has nothing playing", async () => {
+      const { playbackMode } = await import("./playbackMode");
+
+      playbackMode.setMode("remote", "session-123");
+      currentSelectedSession = { id: "session-123", nowPlayingItem: null, playState: null };
+
+      await playbackMode.transferToLocal();
+
+      expect(mockInvoke).not.toHaveBeenCalledWith("player_play_tracks", expect.anything());
+      const state = get(playbackMode);
+      expect(state.mode).toBe("local");
+      expect(state.remoteSessionId).toBeNull();
+    });
+  });
+
   describe("clearError", () => {
     it("should clear transfer error", async () => {
       const { playbackMode } = await import("./playbackMode");