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.ts

@@ -0,0 +1,103 @@
+import { Post, SourceKind } from '../types';
+import { Tab } from './routing';
+
+/**
+ * Which posts each profile tab shows.
+ *
+ * Instagram's profile grid holds everything the account posted — photos,
+ * carousels and reels alike — and the Reels tab is a *filtered view* of that
+ * same set rather than a separate one. So a reel belongs in both tabs, and
+ * only the Reels tab does any filtering.
+ *
+ * Kept pure and separate from App.tsx so the reel heuristic and the
+ * duplicate-copy rules can be tested directly.
+ */
+
+/**
+ * The shortcode shared by every copy of a post, regardless of which source
+ * directory it came from. Sidecar ids are directory-scoped
+ * (`4utumn07 - reels/Cq8LrxSJAJE`); the trailing segment is the shortcode.
+ */
+const shortcode = (post: Post): string => post.id.split('/').pop() ?? post.id;
+
+/**
+ * True when the archive has a `- reels` sidecar directory, i.e. it states
+ * outright which posts are reels.
+ */
+export const hasReelSource = (posts: Post[]): boolean => posts.some(p => p.source === 'reels');
+
+/**
+ * Build the reel test for an archive.
+ *
+ * Instagram's own marker is `product_type: "clips"` on the post's GraphQL
+ * node, but only Instaloader archives carry that metadata, and only on newer
+ * captures — JDownloader grabs are media plus a caption `.txt` and nothing
+ * else (see docs/jdownloader.md). So:
+ *
+ *   - archives with a `- reels` directory are believed outright;
+ *   - everything else falls back to treating a lone video as a reel.
+ *
+ * The fallback is a guess: it cannot tell a reel from an ordinary feed video
+ * or an old IGTV upload, all three of which are plain `GraphVideo` nodes
+ * distinguished only by `product_type`.
+ */
+export const makeIsReel = (posts: Post[]): ((post: Post) => boolean) => (
+  hasReelSource(posts)
+    ? (post: Post) => post.source === 'reels'
+    : (post: Post) => post.media.length === 1 && post.media[0]?.type === 'video'
+);
+
+/** Preference order when the same post was fetched into more than one directory. */
+const SOURCE_RANK: Record<SourceKind, number> = { reels: 0, posts: 1, stories: 2, highlight: 3 };
+
+const rankOf = (post: Post): number => SOURCE_RANK[post.source ?? 'posts'];
+
+/**
+ * Collapse copies of one post that were fetched into more than one directory.
+ *
+ * The JDownloader flow crawls a profile URL and its `/reels/` URL separately
+ * because the profile page misses some reels — so the two overlap, and a reel
+ * present in both lands on disk twice. Those become two posts with distinct
+ * directory-scoped ids, which the grid would happily render side by side.
+ *
+ * The reels-source copy wins, so the surviving post still reports
+ * `source: 'reels'` and both the Reels tab and `tabForSource` recognise it.
+ *
+ * Only safe because callers pass the grid's posts, which exclude stories and
+ * highlights — a shortcode may legitimately appear in both the profile and a
+ * highlight, and those must stay distinct.
+ */
+export const dedupePostCopies = (posts: Post[]): Post[] => {
+  const winners = new Map<string, Post>();
+
+  for (const post of posts) {
+    const code = shortcode(post);
+    const existing = winners.get(code);
+    if (!existing || rankOf(post) < rankOf(existing)) winners.set(code, post);
+  }
+
+  // Preserve input order, keyed on the winner so ordering does not depend on
+  // which copy happened to be scanned first.
+  const emitted = new Set<string>();
+  const result: Post[] = [];
+  for (const post of posts) {
+    const code = shortcode(post);
+    if (emitted.has(code)) continue;
+    emitted.add(code);
+    result.push(winners.get(code)!);
+  }
+  return result;
+};
+
+/**
+ * The posts a tab displays.
+ *
+ * `posts` must already exclude stories and highlights (App passes `allPosts`).
+ */
+export const postsForTab = (posts: Post[], tab: Tab): Post[] => {
+  if (tab === 'saved') return [];
+
+  const unique = dedupePostCopies(posts);
+  if (tab === 'posts') return unique;
+  return unique.filter(makeIsReel(posts));
+};