test: enrich coverage for queryKeys, BaseQueryStore, and BatchFontStore

- queryKeys: add mutation-safety test for batch(), key hierarchy tests
  (list/batch/detail keys rooted in their parent base keys), and
  unique-key test for different detail IDs
- BaseQueryStore: add initial-state test (data undefined, isError false
  before any fetch resolves)
- BatchFontStore: add FontResponseError type assertion on malformed
  response, null error assertion on success, and setIds([]) disables
  query and returns empty fonts without triggering a fetch

src/entities/Font/model/store/batchFontStore.test.ts

@@ -8,7 +8,10 @@ import {
     vi,
 } from 'vitest';
 import * as api from '../../api/proxy/proxyFonts';
-import { FontNetworkError } from '../../lib/errors/errors';
+import {
+    FontNetworkError,
+    FontResponseError,
+} from '../../lib/errors/errors';
 import { BatchFontStore } from './batchFontStore.svelte';
 
 describe('BatchFontStore', () => {
@@ -58,6 +61,31 @@ describe('BatchFontStore', () => {
             vi.spyOn(api, 'fetchFontsByIds').mockResolvedValue(null as any);
             const store = new BatchFontStore(['a']);
             await vi.waitFor(() => expect(store.isError).toBe(true), { timeout: 1000 });
+            expect(store.error).toBeInstanceOf(FontResponseError);
+        });
+
+        it('should have null error in success state', async () => {
+            const fonts = [{ id: 'a' }] as any[];
+            vi.spyOn(api, 'fetchFontsByIds').mockResolvedValue(fonts);
+            const store = new BatchFontStore(['a']);
+            await vi.waitFor(() => expect(store.fonts).toEqual(fonts), { timeout: 1000 });
+            expect(store.error).toBeNull();
+        });
+    });
+
+    describe('Disable Behavior', () => {
+        it('should return empty fonts and not fetch when setIds is called with empty array', async () => {
+            const fonts1 = [{ id: 'a' }] as any[];
+            const spy = vi.spyOn(api, 'fetchFontsByIds').mockResolvedValueOnce(fonts1);
+
+            const store = new BatchFontStore(['a']);
+            await vi.waitFor(() => expect(store.fonts).toEqual(fonts1), { timeout: 1000 });
+
+            spy.mockClear();
+            store.setIds([]);
+
+            await vi.waitFor(() => expect(store.fonts).toEqual([]), { timeout: 1000 });
+            expect(spy).not.toHaveBeenCalled();
         });
     });