feat: show reels in the profile grid, as Instagram does

The Posts tab filtered reels out, so the grid was not the archive — it
was the archive minus its videos. For `for.heejin` that hid 533 of 1225
posts; for `loonatheworld`, 1100 of 3813. On Instagram the grid holds
everything and the Reels tab is a filtered view of that same set.

Extract the tab logic to src/lib/post-tabs.ts so the reel heuristic is
testable outside the component, and add dedupePostCopies: the jd2 flow
crawls the profile URL and the /reels URL separately because the profile
page misses some reels, so the two overlap and a reel can land on disk
twice. Those are two posts with distinct directory-scoped ids, which the
grid would now render side by side; the reels-source copy wins so the
survivor is still recognised as a reel.

Deciding what *is* a reel stays a guess for most archives. Instagram
marks it with product_type ("clips" vs "feed" vs "igtv" — all three are
GraphVideo, and aspect ratio does not separate them), but only newer
Instaloader captures carry it: 1101 of gibiofficial's 5919 sidecars, and
only 2 marked clips. JDownloader archives carry none, so those still
fall back to treating a lone video as a reel.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/lib/post-tabs.test.ts

@@ -0,0 +1,100 @@
+import { describe, expect, it } from 'vitest';
+import { dedupePostCopies, hasReelSource, makeIsReel, postsForTab } from './post-tabs';
+import { MediaFile, Post } from '../types';
+
+const media = (type: MediaFile['type'], index = 1): MediaFile => ({
+  name: `f${index}.${type === 'video' ? 'mp4' : 'jpg'}`,
+  path: `d/f${index}`, url: '', type, index,
+});
+
+const post = (id: string, opts: Partial<Post> = {}): Post => ({
+  id, date: '2024-01-01', username: 'u', caption: '', media: [media('image')], thumbnail: '', ...opts,
+});
+
+const video = (id: string, opts: Partial<Post> = {}) => post(id, { media: [media('video')], ...opts });
+const carousel = (id: string, opts: Partial<Post> = {}) =>
+  post(id, { media: [media('image', 1), media('video', 2)], ...opts });
+
+describe('hasReelSource', () => {
+  it('is false for an archive with no reels directory', () => {
+    expect(hasReelSource([post('A'), video('B')])).toBe(false);
+  });
+
+  it('is true once any post came from a reels directory', () => {
+    expect(hasReelSource([post('A'), video('u - reels/B', { source: 'reels' })])).toBe(true);
+  });
+});
+
+describe('makeIsReel', () => {
+  it('believes the reels directory when there is one', () => {
+    const posts = [video('A'), video('u - reels/B', { source: 'reels' })];
+    const isReel = makeIsReel(posts);
+    // A is a lone video too, but the archive states which posts are reels.
+    expect(isReel(posts[0])).toBe(false);
+    expect(isReel(posts[1])).toBe(true);
+  });
+
+  it('falls back to the lone-video heuristic without one', () => {
+    const posts = [post('A'), video('B'), carousel('C')];
+    const isReel = makeIsReel(posts);
+    expect(posts.map(isReel)).toEqual([false, true, false]);
+  });
+});
+
+describe('dedupePostCopies', () => {
+  it('leaves distinct posts alone', () => {
+    const posts = [post('A'), video('B')];
+    expect(dedupePostCopies(posts).map(p => p.id)).toEqual(['A', 'B']);
+  });
+
+  it('collapses a reel fetched into both the profile and the reels directory', () => {
+    const posts = [video('B'), video('u - reels/B', { source: 'reels' })];
+    const deduped = dedupePostCopies(posts);
+    expect(deduped).toHaveLength(1);
+    // The reels copy wins, so the survivor is still recognised as a reel.
+    expect(deduped[0].source).toBe('reels');
+  });
+
+  it('picks the reels copy regardless of scan order', () => {
+    const profileCopy = video('B');
+    const reelCopy = video('u - reels/B', { source: 'reels' });
+    expect(dedupePostCopies([profileCopy, reelCopy])[0].source).toBe('reels');
+    expect(dedupePostCopies([reelCopy, profileCopy])[0].source).toBe('reels');
+  });
+
+  it('keeps the position of the first copy seen', () => {
+    const posts = [post('A'), video('B'), post('C'), video('u - reels/B', { source: 'reels' })];
+    expect(dedupePostCopies(posts).map(p => p.id.split('/').pop())).toEqual(['A', 'B', 'C']);
+  });
+});
+
+describe('postsForTab', () => {
+  it('shows reels in the profile grid, as Instagram does', () => {
+    const posts = [post('A'), video('u - reels/B', { source: 'reels' })];
+    expect(postsForTab(posts, 'posts').map(p => p.id)).toEqual(['A', 'u - reels/B']);
+  });
+
+  it('shows the same reel in both tabs', () => {
+    const posts = [post('A'), video('u - reels/B', { source: 'reels' })];
+    const inGrid = postsForTab(posts, 'posts').map(p => p.id);
+    const inReels = postsForTab(posts, 'reels').map(p => p.id);
+    expect(inReels).toEqual(['u - reels/B']);
+    expect(inGrid).toContain('u - reels/B');
+  });
+
+  it('shows a duplicated reel once in the grid, not twice', () => {
+    const posts = [post('A'), video('B'), video('u - reels/B', { source: 'reels' })];
+    expect(postsForTab(posts, 'posts')).toHaveLength(2);
+    expect(postsForTab(posts, 'reels')).toHaveLength(1);
+  });
+
+  it('treats lone videos as reels for archives with no reels directory', () => {
+    const posts = [post('A'), video('B'), carousel('C')];
+    expect(postsForTab(posts, 'posts').map(p => p.id)).toEqual(['A', 'B', 'C']);
+    expect(postsForTab(posts, 'reels').map(p => p.id)).toEqual(['B']);
+  });
+
+  it('has nothing saved', () => {
+    expect(postsForTab([post('A')], 'saved')).toEqual([]);
+  });
+});