fix(mobile): hide empty mobile reply backlink wrapper (#1060)

getRenderableMobileBacklinks() now filters mobile backlinks down to replies that can actually render, so ReplyBacklinks only mounts mobileReplyBacklinks when there is visible content. This adds a regression test for the gap where a newly published reply exists before it receives its post number.

src/lib/utils/__tests__/reply-backlink-utils.test.ts

@@ -0,0 +1,44 @@
+import type { Comment } from '@bitsocialnet/bitsocial-react-hooks';
+import { describe, expect, it } from 'vitest';
+import { getRenderableMobileBacklinks } from '../reply-backlink-utils';
+
+const createReply = (overrides: Partial<Comment> = {}) =>
+  ({
+    cid: 'reply-cid',
+    parentCid: 'target-cid',
+    subplebbitAddress: 'music.eth',
+    ...overrides,
+  }) as Comment;
+
+describe('getRenderableMobileBacklinks', () => {
+  it('does not report mobile reply backlinks until a renderable backlink exists', () => {
+    const unpublishedReply = createReply({
+      number: undefined,
+    });
+
+    const beforePublish = getRenderableMobileBacklinks({
+      cid: 'target-cid',
+      parentCid: 'op-cid',
+      quotedByMap: new Map([['target-cid', [unpublishedReply]]]),
+      directRepliesByParentCid: new Map([['target-cid', [unpublishedReply]]]),
+    });
+
+    expect(beforePublish.directReplyBacklinks).toHaveLength(0);
+    expect(beforePublish.quotedReplyBacklinks).toHaveLength(0);
+
+    const publishedReply = createReply({
+      cid: 'published-reply-cid',
+      number: 42,
+    });
+
+    const afterPublish = getRenderableMobileBacklinks({
+      cid: 'target-cid',
+      parentCid: 'op-cid',
+      quotedByMap: new Map([['target-cid', [publishedReply]]]),
+      directRepliesByParentCid: new Map([['target-cid', [publishedReply]]]),
+    });
+
+    expect(afterPublish.directReplyBacklinks).toEqual([publishedReply]);
+    expect(afterPublish.quotedReplyBacklinks).toHaveLength(0);
+  });
+});