feat(comparisonStore): add isLoading getter

src/widgets/ComparisonSlider/model/stores/comparisonStore.svelte.ts

@@ -136,6 +136,10 @@ class ComparisonStore {
         return !!this.#fontA && !!this.#fontB;
     }
 
+    get isLoading() {
+        return this.#isRestoring;
+    }
+
     /**
      * Public initializer (optional, as constructor starts it)
      * Kept for compatibility if manual re-init is needed