android: the handoff — the pending rounds, the pipeline, and what is unverified

Everything written this session that has not been through the device: rounds 43
to 48 (each patch adversarially verified, 43's transient-notice expectation
fixed), a partial round 49, the pipeline scripts, the Android Auto design and
the icon comparison mock. Also the two harness changes that were never A/B'd —
adaptive waits, which may only shorten a declared wait and never lengthen it,
and a ship that runs the mock walk and the deploy at the same time. The A/B and
its 255-step baseline are in handoff/tools; main stays at what the phone has
actually walked.

handoff/rounds/ins-r25-popular.txt

@@ -0,0 +1,15 @@
+/** Popular on its own — the desktop's fast lane (`catalog_artist_popular`).
+ *  It waits on nothing but the linked MBID and one Last.fm call, so the
+ *  section can paint while the full page is still being built; the page's
+ *  own list wins once it lands (the same order, from the same inputs), and
+ *  this one stays for an artist whose page came back with no Popular. */
+export function loadPopular(id) {
+    if (id == null || catalog.popular[id]) return;
+    catalog.popular[id] = { status: "loading", tracks: [] };
+    api.catalogArtistPopular(id).then(
+        (tracks) => { catalog.popular[id] = { status: "ready", tracks: tracks ?? [] }; },
+        () => { catalog.popular[id] = { status: "error", tracks: [] }; },
+    );
+}
+
+/** A portrait for a byline — the same identity rule, search only. */