artist page: always open at the top

.content is the app's one scroll pane and it outlives the view swap, so its
scrollTop was inherited by whatever loaded next: leave one artist 900px down
their discography, open another, and you arrived 900px down the new one —
mid-grid, hero already squeezed into the bar, with no hint the page had a top.

Reset it on catalog.artistOpenSeq, a counter bumped once per openCatalogArtist
call, rather than on the artist's id. The id cannot distinguish a re-open of the
artist already on screen — clicking their name from Now Playing while parked
deep in their own page, where nothing moved and the click read as dead — from no
navigation at all. Nor can this key on the page object: the cold path replaces
it stage by stage under the same id, which would haul a reader back to the top
mid-read. The counter bumps once per open and never per stage.

The bump sits after openCatalogArtist's invalid-id bail-out, so a request that
never opens anything cannot scroll the page the reader is still on.

Verified live: three artist-to-artist hops parked at 1222 each land at 0 and
stay 0 through every cold stage; re-opening the artist already on screen from
1070 lands at 0; mounting from another view with the pane genuinely parked at
1500 mounts at 0; and a reader parked at 600 on the artist they are already on
holds at 600 through six seconds of stage churn.

src/views/CatalogArtist.svelte

@@ -113,6 +113,25 @@
         return () => clearTimeout(t);
     });
 
+    // Every artist page opens at the top. `.content` is the app's ONE scroll
+    // pane and it outlives the view swap, so its scrollTop carried over: leave
+    // one artist 900px down its discography, open another, and you landed 900px
+    // down the new one — mid-grid, hero already squeezed into the bar, with no
+    // hint the page had a top.
+    // Keyed on catalog.artistOpenSeq, NOT the artist's id. The id cannot tell a
+    // re-open of the artist already on screen (clicking their name from Now
+    // Playing while parked deep in their own page — nothing moved) from no
+    // navigation at all. It also cannot be keyed on `page`: the cold path
+    // replaces that object stage by stage under the same id, which would haul a
+    // reader back to the top mid-read. The seq bumps once per open and never
+    // per stage. Ask for the pane BY NAME — the same rule scrollPaneFor()
+    // follows, and for the same reason.
+    $effect(() => {
+        void catalog.artistOpenSeq;
+        const pane = document.querySelector(".content");
+        if (pane) pane.scrollTop = 0;
+    });
+
     // THE HERO PIPELINE (Kyle, 2026-07-24 — the approved configuration,
     // now unconditional):
     //   - Crossfade twins: the main-thread blur filter rides on the hero