feat(discover): Artists|Albums tabs on /discover

Suggested artists and Suggested albums were stacked sections; make them
tabs like /lastfm (.tabs bar + count badge). Discover-now/freshness and
Find-similar stay above the tabs.

The Albums tab filters to full-length albums (isFullAlbum) — a client-side
stopgap that hides any pre-D1 singles/EP suggestions still in the DB (new
sweeps already filter server-side via discover.albumsOnly).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/app/discover/discover-client.tsx

@@ -15,11 +15,22 @@ type Suggestion = {
   artistName: string;
   rgMbid: string | null;
   album: string | null;
+  primaryType: string | null;
+  secondaryTypes: string[];
   score: number;
   seedCount: number;
   sources: string[];
 };
 
+type Tab = "Artists" | "Albums";
+
+/** Only full-length albums belong in Suggested albums — hide singles/EPs and
+ *  secondary-type releases (live/comp). New sweeps already filter server-side
+ *  (discover.albumsOnly); this also sweeps any pre-filter rows still in the DB. */
+function isFullAlbum(s: Suggestion): boolean {
+  return (s.primaryType ?? "Album") === "Album" && (s.secondaryTypes?.length ?? 0) === 0;
+}
+
 /** "just now" / "3h ago" / "2d ago" — timeAgo has no suffix, so add one (except "just now"). */
 function agoLabel(value: string): string {
   const a = timeAgo(value, Date.now());
@@ -43,6 +54,9 @@ export function DiscoverClient() {
   const [followedSimilar, setFollowedSimilar] = useState<Set<string>>(new Set());
   const [artistModal, setArtistModal] = useState<{ mbid: string; name: string } | null>(null);
   const [albumModal, setAlbumModal] = useState<Suggestion | null>(null);
+  const [tab, setTab] = useState<Tab>("Artists");
+
+  const albums = feed.albums.filter(isFullAlbum);
 
   const loadFeed = useCallback(async () => {
     setFeed(await (await fetch("/api/discover")).json());
@@ -172,8 +186,19 @@ export function DiscoverClient() {
         </ul>
       ) : null}
 
-      <SectionHeader title="Suggested artists" note={`${feed.artists.length}`} />
-      {feed.artists.length === 0 ? (
+      <div className="tabs">
+        <button className={`tab${tab === "Artists" ? " active" : ""}`} onClick={() => setTab("Artists")}>
+          Suggested artists
+          <span className="n">{feed.artists.length}</span>
+        </button>
+        <button className={`tab${tab === "Albums" ? " active" : ""}`} onClick={() => setTab("Albums")}>
+          Suggested albums
+          <span className="n">{albums.length}</span>
+        </button>
+      </div>
+
+      {tab === "Artists" ? (
+        feed.artists.length === 0 ? (
         <p className="muted-note">No suggestions yet — run Discover, or follow a few artists to seed it.</p>
       ) : (
         <ul className="list">
@@ -204,14 +229,12 @@ export function DiscoverClient() {
             </li>
           ))}
         </ul>
-      )}
-
-      <SectionHeader title="Suggested albums" note={`${feed.albums.length}`} />
-      {feed.albums.length === 0 ? (
+      )
+      ) : albums.length === 0 ? (
         <p className="muted-note">No album suggestions yet.</p>
       ) : (
         <ul className="list">
-          {feed.albums.map((s) => (
+          {albums.map((s) => (
             <li key={s.id} className="list-row">
               <div className="main">
                 <button className="disco-open" onClick={() => setAlbumModal(s)} aria-label={`Open ${s.album ?? ""}`}>