fix(reader): make annotation toolbar customization apply to all books (#4760)

The customized annotation toolbar only took effect in the book where it
was changed, instead of applying to every book.

Root cause: serializeConfig decided which per-book view settings to
persist as overrides using a reference check (globalViewSettings[key]
!== value). It deep-clones the config first, so array-valued settings
like annotationToolbarItems are always a fresh reference and were stored
as a per-book override on every save (each progress autosave). On reopen
the per-book override shadowed the global value, so a global toolbar
change never reached already-opened books.

Compare view-setting values by content, not reference, so array/object
settings equal to the global value are no longer persisted per-book. This
also fixes the same latent issue for paragraphMode, proofreadRules,
ttsHighlightOptions and noteExportConfig.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/readest-app/src/__tests__/utils/serializer.test.ts

@@ -108,6 +108,43 @@ describe('BookConfig serialization', () => {
     expect(tombstone.deletedAt).toBeTruthy();
   });
 
+  it('does not persist an array view setting that equals the global value', () => {
+    // Array/object view settings must be compared by value, not reference —
+    // otherwise annotationToolbarItems (an array) is stored as a per-book override on
+    // every save, shadowing later global changes (the customize-toolbar bug).
+    const global = {
+      ...globalViewSettings,
+      annotationToolbarItems: ['highlight', 'annotate', 'copy'],
+    } as unknown as ViewSettings;
+    const config: BookConfig = {
+      updatedAt: 1,
+      // Same content as global but a distinct array reference, as produced by the
+      // load -> merge -> serialize round-trip.
+      viewSettings: {
+        annotationToolbarItems: ['highlight', 'annotate', 'copy'],
+      } as Partial<ViewSettings>,
+    };
+
+    const parsed = JSON.parse(serializeConfig(config, global, defaultSearchConfig));
+
+    expect(parsed.viewSettings.annotationToolbarItems).toBeUndefined();
+  });
+
+  it('persists an array view setting that differs from the global value', () => {
+    const global = {
+      ...globalViewSettings,
+      annotationToolbarItems: ['highlight', 'annotate', 'copy'],
+    } as unknown as ViewSettings;
+    const config: BookConfig = {
+      updatedAt: 1,
+      viewSettings: { annotationToolbarItems: ['copy'] } as Partial<ViewSettings>,
+    };
+
+    const parsed = JSON.parse(serializeConfig(config, global, defaultSearchConfig));
+
+    expect(parsed.viewSettings.annotationToolbarItems).toEqual(['copy']);
+  });
+
   it('does not migrate annotations when schemaVersion is already 2', () => {
     const config = deserializeConfig(
       JSON.stringify({

apps/readest-app/src/utils/serializer.ts

@@ -14,6 +14,15 @@ export const serializeRawConfig = (config: Partial<BookConfig>): string => {
   return JSON.stringify(stampBookConfigSchema(config));
 };
 
+// Compare a per-book view-setting value with the global one by value, not
+// reference. serializeConfig deep-clones the config first, so array/object
+// settings (e.g. annotationToolbarItems) are always fresh references; a reference
+// check would persist them as per-book overrides even when identical to global,
+// which then shadows later global changes on reopen. Primitives short-circuit;
+// the JSON compare covers arrays and plain config objects (all JSON-serializable).
+const isSameViewSettingValue = (a: unknown, b: unknown): boolean =>
+  a === b || JSON.stringify(a) === JSON.stringify(b);
+
 export const serializeConfig = (
   config: BookConfig,
   globalViewSettings: ViewSettings,
@@ -35,7 +44,7 @@ export const serializeConfig = (
   const searchConfig = (config.searchConfig ?? {}) as Partial<BookSearchConfig>;
   config.viewSettings = Object.entries(viewSettings).reduce(
     (acc: Partial<Record<keyof ViewSettings, unknown>>, [key, value]) => {
-      if (globalViewSettings[key as keyof ViewSettings] !== value) {
+      if (!isSameViewSettingValue(globalViewSettings[key as keyof ViewSettings], value)) {
         acc[key as keyof ViewSettings] = value;
       }
       return acc;