feat: add appMode preference (clipper/player) with persistence

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/lib/stores/preferences.test.ts

@@ -0,0 +1,38 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+
+// Mock the Tauri store before importing the module under test
+vi.mock('@tauri-apps/plugin-store', () => {
+  const mockStore = {
+    get: vi.fn().mockResolvedValue(null),
+    set: vi.fn().mockResolvedValue(undefined),
+    save: vi.fn().mockResolvedValue(undefined),
+  };
+  return {
+    load: vi.fn().mockResolvedValue(mockStore),
+    Store: vi.fn(),
+  };
+});
+
+describe('preferences store — appMode', () => {
+  beforeEach(() => {
+    vi.resetModules();
+  });
+
+  it('defaults appMode to clipper', async () => {
+    const { preferences } = await import('$lib/stores/preferences.svelte');
+    expect(preferences.appMode).toBe('clipper');
+  });
+
+  it('setAppMode updates appMode to player', async () => {
+    const { preferences, setAppMode } = await import('$lib/stores/preferences.svelte');
+    await setAppMode('player');
+    expect(preferences.appMode).toBe('player');
+  });
+
+  it('setAppMode updates appMode back to clipper', async () => {
+    const { preferences, setAppMode } = await import('$lib/stores/preferences.svelte');
+    await setAppMode('player');
+    await setAppMode('clipper');
+    expect(preferences.appMode).toBe('clipper');
+  });
+});