fix(bulk-edit): auto-clear selection store when leaving /documents and /enrich

Felix C4 — bulkSelectionStore is module-singleton; before this change it
silently followed the user from /documents to /persons / /admin / etc.,
then reappeared as a stale count when they wandered back. Root +layout.svelte
now watches page.url.pathname and clears the store the moment the user
leaves the two routes that surface BulkSelectionBar.

Refs #225, PR #331

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/routes/+layout.svelte

@@ -10,6 +10,7 @@ import AppNav from './AppNav.svelte';
 import UserMenu from './UserMenu.svelte';
 import ConfirmDialog from '$lib/components/ConfirmDialog.svelte';
 import { provideConfirmService } from '$lib/services/confirm.svelte.js';
+import { bulkSelectionStore } from '$lib/stores/bulkSelection.svelte';
 
 let { children, data } = $props();
 
@@ -17,6 +18,22 @@ let { children, data } = $props();
 // ConfirmDialog below reads it via getConfirmService() and renders the <dialog>.
 provideConfirmService();
 
+// Auto-clear the bulk-selection store when the user leaves the routes that
+// surface the BulkSelectionBar. Without this the selection silently follows
+// the user to /persons / /admin etc. and reappears as a stale 3-doc count
+// when they wander back to /documents — Felix C4 on PR #331.
+$effect(() => {
+	const path = page.url.pathname;
+	const inBulkContext =
+		path === '/documents' ||
+		path.startsWith('/documents/') ||
+		path === '/enrich' ||
+		path.startsWith('/enrich/');
+	if (!inBulkContext && bulkSelectionStore.size > 0) {
+		bulkSelectionStore.clear();
+	}
+});
+
 const isAdmin = $derived(
 	data?.user?.groups?.some((g: { permissions: string[] }) => g.permissions.includes('ADMIN'))
 );