feat(plex): redesign browse tiles — 2-poster montage top, readable label band

The full-bleed 4-poster collage drowned the on-tile text. Split PosterTile in two: the top
half shows up to 2 montage posters, the bottom half is a solid colour-hash band that carries
the label, so the text is always readable. Genre tiles drop the count (just the label now);
collection tiles show the name on one truncated line plus a sub-line of item count · total
runtime. A group with no art falls back to an all-colour tile.

Backend: `/collections` cards gain `total_runtime_s` (a new `runtime_by_key` grouped sum) and
their montage art is capped at 2. Frontend: PosterTile reworked; a `collectionMeta` helper
builds the count·runtime sub-line via the existing formatRuntime.

Verified live: collection and genre tiles render 2 posters over a readable colour band with
the right sub-lines; colour fallback intact for art-less groups.

Gate: tsc/lint/knip/prettier clean, 423 vitest; backend ruff clean, collections tests green
(+ a new art/runtime assertion).

frontend/src/components/PlexDiscover.tsx

@@ -204,9 +204,8 @@ export default function PlexDiscover({
                 key={g.value}
                 title={g.value}
                 art={g.art}
-                topRight={<span className="text-2xs text-white/80 drop-shadow">{g.count}</span>}
                 onClick={() => onGenre(g.value)}
-                className="h-20"
+                className="h-24"
               />
             ))}
           </div>

frontend/src/components/PosterTile.tsx

@@ -1,9 +1,10 @@
 import { type ReactNode } from "react";
 import { hueOf, hueTileGradient } from "../lib/hueTile";
 
-// A browse tile: a 2×2 collage of the group's top poster art (served from /api/plex/image/{key}) under
-// a dark scrim with the label, falling back to a color hash when the group has no art — so a tile never
-// renders blank. Shared by the Discover genre tiles and the Playlist/Collection browse tiles.
+// A browse tile split in two: the TOP half shows up to 2 montage posters (from /api/plex/image/{key}),
+// the BOTTOM half is a solid colour-hash band that carries the label — so the text is always readable
+// (a full-bleed poster collage drowned it). A group with no art falls back to an all-colour tile, never
+// blank. Shared by the Discover genre tiles and the Playlist/Collection browse tiles.
 export default function PosterTile({
   title,
   subtitle,
@@ -13,24 +14,29 @@ export default function PosterTile({
   className,
 }: {
   title: string;
-  subtitle?: ReactNode; // a bottom sub-line under the title (e.g. "12 items")
-  topRight?: ReactNode; // top-right corner content (a count, or an icon)
-  art?: string[]; // up to 4 poster rating_keys; fewer/none falls back to the color hash
+  subtitle?: ReactNode; // a bottom sub-line under the title (e.g. "12 items · 4h 30m")
+  topRight?: ReactNode; // top-right corner content on the colour band (e.g. an icon)
+  art?: string[]; // up to 2 poster rating_keys; fewer/none falls back to the colour hash
   onClick: () => void;
   className?: string; // caller sets the height (e.g. "h-20" / "h-28")
 }) {
-  const posters = (art ?? []).slice(0, 4);
+  const posters = (art ?? []).slice(0, 2);
+  const band = hueTileGradient(hueOf(title));
   return (
     <button
       type="button"
       onClick={onClick}
       title={title}
-      className={`glass-hover group relative flex flex-col justify-end overflow-hidden rounded-xl text-left transition ${className ?? ""}`}
-      style={posters.length === 0 ? { background: hueTileGradient(hueOf(title)) } : undefined}
+      className={`glass-hover group relative flex flex-col overflow-hidden rounded-xl text-left transition ${className ?? ""}`}
     >
-      {posters.length > 0 && (
-        <div className="absolute inset-0 grid grid-cols-2 grid-rows-2">
-          {Array.from({ length: 4 }).map((_, i) =>
+      {/* Top half: 2 montage posters, or the colour hash when a group has no art. */}
+      <div
+        className="grid h-1/2 min-h-0 grid-cols-2"
+        aria-hidden
+        style={posters.length === 0 ? { background: band } : undefined}
+      >
+        {posters.length > 0 &&
+          [0, 1].map((i) =>
             posters[i] ? (
               <img
                 key={i}
@@ -43,14 +49,12 @@ export default function PosterTile({
               <div key={i} style={{ background: hueTileGradient(hueOf(title + i)) }} />
             ),
           )}
-        </div>
-      )}
-      <div className="absolute inset-0 bg-gradient-to-t from-black/75 via-black/10 to-transparent" />
-      {/* After the scrim in DOM order → paints above it without a z-index token. */}
-      {topRight != null && <span className="absolute right-2 top-2">{topRight}</span>}
-      <div className="relative p-3">
-        <div className="line-clamp-2 text-sm font-semibold text-white drop-shadow">{title}</div>
-        {subtitle != null && <div className="text-2xs text-white/80">{subtitle}</div>}
+      </div>
+      {/* Bottom half: solid colour band — the label lives here so it stays readable over any art. */}
+      <div className="relative flex flex-1 flex-col justify-end p-2.5" style={{ background: band }}>
+        {topRight != null && <span className="absolute right-2 top-2">{topRight}</span>}
+        <div className="truncate text-sm font-semibold text-white drop-shadow">{title}</div>
+        {subtitle != null && <div className="truncate text-2xs text-white/80">{subtitle}</div>}
       </div>
     </button>
   );

frontend/src/components/plexBrowseLists.tsx

@@ -1,13 +1,25 @@
 import { useState } from "react";
 import { useTranslation } from "react-i18next";
+import type { TFunction } from "i18next";
 import { useQuery } from "@tanstack/react-query";
-import { Layers, ListMusic } from "lucide-react";
+import { ListMusic } from "lucide-react";
 import { qk } from "../lib/queryKeys";
-import { api } from "../lib/api";
+import { api, type PlexCollection } from "../lib/api";
+import { formatRuntime } from "../lib/format";
 import { useDebounced } from "../lib/useDebounced";
 import { LoadingState, StateMessage } from "./QueryState";
 import PosterTile from "./PosterTile";
 
+// A collection tile's sub-line: item count · total runtime (each dropped when unknown, e.g. show-only
+// collections have no movie runtime).
+function collectionMeta(c: PlexCollection, t: TFunction): string {
+  const parts: string[] = [];
+  if (c.child_count != null) parts.push(t("plex.browse.items", { count: c.child_count }));
+  const rt = formatRuntime(c.total_runtime_s);
+  if (rt) parts.push(rt);
+  return parts.join(" · ");
+}
+
 // The Playlist / Collection browse surfaces reached from the header pill (Piece 2): a grid of tiles,
 // each a way INTO that area — a playlist tile opens the playlist view, a collection tile filters the
 // title grid by that collection. Both reuse the existing list endpoints (plexPlaylists / plexCollections
@@ -87,10 +99,7 @@ export function PlexCollectionsBrowse({ onPick }: { onPick: (id: string, title:
               key={c.id}
               title={c.title}
               art={c.art}
-              subtitle={
-                c.child_count != null ? t("plex.browse.items", { count: c.child_count }) : undefined
-              }
-              topRight={<Layers className="h-4 w-4 text-white/80 drop-shadow" />}
+              subtitle={collectionMeta(c, t)}
               onClick={() => onPick(c.id, c.title)}
               className="h-28"
             />