android: the catalog's numbers — Popular's own lane, a count per row, the artist's photo

Popular is asked on its own as well as with the page, so the section can
paint before the full page is built and an artist whose page came back
with none still gets one. A catalog record's rows that the album's own
artist anchor found no count for — a feature's guest, a compilation's
stranger — get the deferred Last.fm pass by their own artist id. The
artist page's ⋯ is its own sheet now: choose a hero photo from this phone,
or put the catalog's own back; set_artist_hero is pick_artist_hero's
install step split out and shared, so the desktop's dialog keeps its door.
You gains the desktop's Refresh artist portraits, and a data: URL is the
image itself in the art gate — a chosen hero comes back from Rust as one,
and the thumbnail fetch used to throw it away.

src/mobile/screens/Artist.svelte

@@ -19,7 +19,7 @@
     import { art, wantArt } from "../art.svelte.js";
     import { player, playEntries, playAlbum } from "../player.svelte.js";
     import { push, openHalf } from "../nav.svelte.js";
-    import { catalog, lookupArtist, artistKey, fans, yearOf, looseTitle, loadExtras, picture } from "../catalog.svelte.js";
+    import { catalog, lookupArtist, artistKey, fans, yearOf, looseTitle, loadExtras, loadPopular, picture } from "../catalog.svelte.js";
     import { resolver, streamSong, streamCatalogAlbum } from "../resolve.svelte.js";
     import { discoTabs, activeYears, latestOf, timelineOf, isUpcoming, SOCIAL_LABEL } from "../disco.js";
     import { shuffled, mmss, ago } from "../util.js";
@@ -64,6 +64,10 @@
         const nm = page?.artist?.name || name;
         if (id != null) untrack(() => loadExtras(id, nm));
     });
+    /* Popular's own lane, asked the moment an id is known — from the
+       search's own row, or from the identity search — so the section can
+       paint before the full page is built */
+    $effect(() => { const id = artistId; if (id != null) untrack(() => loadPopular(id)); });
     const seedSrc = $derived(seedPath ? art[seedPath] : "");
     const heroSrc = $derived(heroUrl ? art[heroUrl] : "");
     const extras = $derived(artistId != null ? catalog.extras[artistId] ?? null : null);
@@ -88,7 +92,11 @@
     });
 
     /* ── Popular ─────────────────────────────────────────────────────── */
-    const popularAll = $derived(page?.popular_tracks ?? []);
+    /* the page's own list once it lands (the same Last.fm order, from the
+       same inputs); the fast lane's until then, and for an artist whose
+       page came back with no Popular at all */
+    const fastPopular = $derived(artistId != null ? catalog.popular[artistId]?.tracks ?? [] : []);
+    const popularAll = $derived(page?.popular_tracks?.length ? page.popular_tracks : fastPopular);
     let showAllPopular = $state(false);
     const popular = $derived((showAllPopular ? popularAll : popularAll.slice(0, 5)).map((t) => ({ t, hit: libByTitle.get(looseTitle(t.title)) || null })));
     const popPeak = $derived(popularAll.reduce((m, t) => Math.max(m, t.listeners || 0), 0));