refactor(Breadcrumb): simplify entity structure and add tests

src/entities/Breadcrumb/index.ts

@@ -1,5 +1,35 @@
+/**
+ * Breadcrumb entity
+ *
+ * Tracks page sections using Intersection Observer with scroll direction
+ * detection. Sections appear in breadcrumbs when scrolling down and exiting
+ * the viewport top.
+ *
+ * @example
+ * ```svelte
+ * <script lang="ts">
+ *   import { scrollBreadcrumbsStore } from '$entities/Breadcrumb';
+ *   import { onMount } from 'svelte';
+ *
+ *   onMount(() => {
+ *     const section = document.getElementById('section');
+ *     if (section) {
+ *       scrollBreadcrumbsStore.add({
+ *         index: 0,
+ *         title: 'Section',
+ *         element: section
+ *       }, 80);
+ *     }
+ *   });
+ * </script>
+ * ```
+ */
+
 export {
-    handleTitleStatusChanged,
+    type NavigationAction,
     scrollBreadcrumbsStore,
 } from './model';
-export { BreadcrumbHeader } from './ui';
+export {
+    BreadcrumbHeader,
+    NavigationWrapper,
+} from './ui';