fix(discover): hide stale singles + replace album set on re-derive

- Client filters the row's album thumbnails to full albums only (hides
  singles/EPs left over from pre-albums-only sweeps).
- Worker: re-deriving an artist deletes its pending album suggestions that are
  no longer picks (stale singles / now-owned), keeping wanted/dismissed rows,
  so the suggestion set self-cleans instead of accumulating.

worker 246, web 189 tests.

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

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

@@ -36,6 +36,12 @@ function similarTo(seeds: string[]): string | null {
   return `Similar to ${shown}${extra > 0 ? ` +${extra} more` : ""}`;
 }
 
+/** Full-length albums only — hide singles/EPs and secondary-type releases (live/comp) that
+ *  pre-date the albums-only derivation and still linger in the DB. */
+function isFullAlbum(a: Album): boolean {
+  return (a.primaryType ?? "Album") === "Album" && (a.secondaryTypes?.length ?? 0) === 0;
+}
+
 /** Human badge for why an album is surfaced. */
 function badgeFor(reason: string | null): string | null {
   if (reason === "newest") return "Newest";
@@ -214,7 +220,9 @@ export function DiscoverClient() {
         <p className="muted-note">No suggestions yet — run Discover, or follow a few artists to seed it.</p>
       ) : (
         <ul className="list">
-          {rows.map((row) => (
+          {rows.map((row) => {
+            const albums = row.albums.filter(isFullAlbum);
+            return (
             <li key={row.artistMbid} className="list-row disco-row">
               <div className="main">
                 <div className="rtitle">
@@ -230,9 +238,9 @@ export function DiscoverClient() {
                 {similarTo(row.seeds) ? <div className="rmeta why">{similarTo(row.seeds)}</div> : null}
               </div>
 
-              {row.albums.length > 0 ? (
+              {albums.length > 0 ? (
                 <div className="disco-albums">
-                  {row.albums.map((a) => (
+                  {albums.map((a) => (
                     <div key={a.id} className="disco-album">
                       <button
                         className="disco-thumb"
@@ -264,7 +272,8 @@ export function DiscoverClient() {
                 ) : null}
               </div>
             </li>
-          ))}
+            );
+          })}
         </ul>
       )}