feat(chronik-row): deep-link COMMENT_ADDED and MENTION_CREATED to comment

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

frontend/src/lib/components/chronik/ChronikRow.svelte

@@ -1,6 +1,7 @@
 <script lang="ts">
 import * as m from '$lib/paraglide/messages.js';
 import { relativeTime } from '$lib/utils/time';
+import { buildCommentHref } from '$lib/utils/commentDeepLink';
 import type { components } from '$lib/generated/api';
 
 type ActivityFeedItemDTO = components['schemas']['ActivityFeedItemDTO'];
@@ -96,10 +97,16 @@ const verbParts: { before: string; after: string } = $derived.by(() => {
 		after: verbText.slice(idx + SENTINEL.length)
 	};
 });
+
+const rowHref: string = $derived(
+	item.commentId
+		? buildCommentHref(item.documentId, item.commentId, item.annotationId ?? null)
+		: `/documents/${item.documentId}`
+);
 </script>
 
 <a
-	href="/documents/{item.documentId}"
+	href={rowHref}
 	data-variant={variant}
 	class="group flex items-start gap-3 rounded-sm p-3 transition-colors hover:bg-canvas focus-visible:ring-2 focus-visible:ring-focus-ring focus-visible:outline-none
 		{variant === 'for-you' ? 'border-l-[3px] border-accent bg-accent-bg/10' : ''}"

frontend/src/lib/components/chronik/ChronikRow.svelte.spec.ts

@@ -133,6 +133,47 @@ describe('ChronikRow', () => {
 		expect(preview?.textContent).not.toContain('Brief vom 12. Juli 1920');
 	});
 
+	// --- deep-link href for comment events ---
+	it('links to /documents/:id?commentId=…&annotationId=… for COMMENT_ADDED', async () => {
+		const item: ActivityFeedItemDTO = {
+			...baseItem,
+			kind: 'COMMENT_ADDED',
+			commentId: 'comment-7',
+			annotationId: 'annot-9'
+		};
+		render(ChronikRow, { item });
+		const link = document.querySelector(
+			'a[href="/documents/doc-1?commentId=comment-7&annotationId=annot-9"]'
+		);
+		expect(link).not.toBeNull();
+	});
+
+	it('links to /documents/:id?commentId=…&annotationId=… for MENTION_CREATED', async () => {
+		const item: ActivityFeedItemDTO = {
+			...baseItem,
+			kind: 'MENTION_CREATED',
+			youMentioned: true,
+			commentId: 'comment-8',
+			annotationId: 'annot-11'
+		};
+		render(ChronikRow, { item });
+		const link = document.querySelector(
+			'a[href="/documents/doc-1?commentId=comment-8&annotationId=annot-11"]'
+		);
+		expect(link).not.toBeNull();
+	});
+
+	it('falls back to bare document href when commentId is absent on a comment row', async () => {
+		// Back-compat for old/missing backend payloads. Still navigates sensibly.
+		const item: ActivityFeedItemDTO = {
+			...baseItem,
+			kind: 'COMMENT_ADDED'
+		};
+		render(ChronikRow, { item });
+		const link = document.querySelector('a[href="/documents/doc-1"]');
+		expect(link).not.toBeNull();
+	});
+
 	// --- robustness: title rendering for edge cases ---
 	it('still renders the row link when documentTitle is an empty string', async () => {
 		// Felix: verbText.indexOf(docTitle) returned 0 for empty titles — the span