refactor(plex): dedupe show/season heroes into DetailHero + WatchedToggle

R12 S4b. PlexShowView and PlexSeasonView were copy-paste siblings — the same
glass hero frame, play/resume poster button, customize-menu slot, and the
mark-watched action button, duplicated verbatim. Two shared components now own
that structure:

- DetailHero: the hero shell (frame + poster button + customize slot + info
  column via children); the season page passes a smaller poster size.
- WatchedToggle: the mark-whole-show/season watched action (icon + label flip);
  the differing labels are props.

Single source of truth for the hero — a future hero change touches one place
instead of two. Gate green (tsc / eslint 0 errors / prettier / knip / vitest 79)
+ self-E2E: the show detail and season detail pages both render their hero,
metadata, actions and watched-toggle identically to before (screenshot-verified;
the stale [hmr] PlexBrowse errors in the console buffer are from an intermediate
edit — the fresh Vite server logs clean).

frontend/src/components/PlexBrowse.tsx

@@ -6,6 +6,7 @@ import {
   useRef,
   useState,
   type CSSProperties,
+  type ReactNode,
 } from "react";
 import { qk } from "../lib/queryKeys";
 import { createPortal } from "react-dom";
@@ -985,6 +986,79 @@ function EpisodeCard({
   );
 }
 
+/** The shared detail-page hero shell used by BOTH the show page and the season subpage (they were
+ * copy-paste siblings). Owns the glass frame, the play/resume poster button, the customize-menu slot,
+ * and the flex info column; the caller passes the customize menu + the title/metadata/actions as
+ * `children`. Poster is slightly larger on the show page (default) than the season page. */
+function DetailHero({
+  thumb,
+  posterTitle,
+  posterDisabled,
+  showPlayOverlay,
+  onPosterClick,
+  posterSizeClass = "w-32 sm:w-44",
+  customizeMenu,
+  children,
+}: {
+  thumb: string;
+  posterTitle: string;
+  posterDisabled: boolean;
+  showPlayOverlay: boolean;
+  onPosterClick: () => void;
+  posterSizeClass?: string;
+  customizeMenu: ReactNode;
+  children: ReactNode;
+}) {
+  return (
+    <div className="glass relative rounded-2xl p-4 sm:p-5 mb-8 flex gap-4 sm:gap-5">
+      <div className="absolute right-3 top-3 z-base">{customizeMenu}</div>
+      <button
+        onClick={onPosterClick}
+        disabled={posterDisabled}
+        className={`group/poster relative ${posterSizeClass} shrink-0 self-start`}
+        title={posterTitle}
+      >
+        <img
+          src={thumb}
+          alt=""
+          className="w-full aspect-2/3 object-cover rounded-xl border border-border"
+        />
+        {showPlayOverlay && (
+          <div className="absolute inset-0 rounded-xl bg-black/40 opacity-0 group-hover/poster:opacity-100 transition grid place-items-center">
+            <Play className="w-10 h-10 text-white" fill="currentColor" />
+          </div>
+        )}
+      </button>
+      <div className="min-w-0 flex-1">{children}</div>
+    </div>
+  );
+}
+
+/** The "mark whole show/season watched" hero action (icon + label flip on state). Verbatim in both
+ * the show and season heroes; the labels differ, so the caller passes both. */
+function WatchedToggle({
+  watched,
+  busy,
+  onToggle,
+  watchedLabel,
+  unwatchedLabel,
+}: {
+  watched: boolean;
+  busy?: boolean;
+  onToggle: () => void;
+  watchedLabel: string;
+  unwatchedLabel: string;
+}) {
+  return (
+    <ActionBtn
+      onClick={onToggle}
+      disabled={busy}
+      icon={watched ? CheckCheck : Check}
+      label={watched ? watchedLabel : unwatchedLabel}
+    />
+  );
+}
+
 function PlexShowView({
   showId,
   onBack,
@@ -1050,8 +1124,13 @@ function PlexShowView({
       ) : (
         <>
           {/* Hero */}
-          <div className="glass relative rounded-2xl p-4 sm:p-5 mb-8 flex gap-4 sm:gap-5">
-            <div className="absolute right-3 top-3 z-base">
+          <DetailHero
+            thumb={show.thumb}
+            posterTitle={show.status === "new" ? t("plex.play") : t("plex.resume")}
+            posterDisabled={!show.resume}
+            showPlayOverlay={!!show.resume}
+            onPosterClick={() => show.resume && onPlay(show.resume.id, allKeys)}
+            customizeMenu={
               <DetailCustomizeMenu
                 artBg={artBg}
                 onToggleArtBg={toggleArtBg}
@@ -1062,25 +1141,8 @@ function PlexShowView({
                 onToggleRelated={toggleRelated}
                 hasRelated={d.related.length > 0}
               />
-            </div>
-            <button
-              onClick={() => show.resume && onPlay(show.resume.id, allKeys)}
-              disabled={!show.resume}
-              className="group/poster relative w-32 sm:w-44 shrink-0 self-start"
-              title={show.status === "new" ? t("plex.play") : t("plex.resume")}
+            }
           >
-              <img
-                src={show.thumb}
-                alt=""
-                className="w-full aspect-2/3 object-cover rounded-xl border border-border"
-              />
-              {show.resume && (
-                <div className="absolute inset-0 rounded-xl bg-black/40 opacity-0 group-hover/poster:opacity-100 transition grid place-items-center">
-                  <Play className="w-10 h-10 text-white" fill="currentColor" />
-                </div>
-              )}
-            </button>
-            <div className="min-w-0 flex-1">
             <h1 className="text-2xl font-semibold leading-tight">{show.title}</h1>
             <div className="mt-1 flex flex-wrap items-center gap-x-2 gap-y-0.5 text-sm text-muted">
               {show.year != null && (
@@ -1137,9 +1199,7 @@ function PlexShowView({
               </div>
             )}
             {show.summary && (
-                <p className="text-sm text-muted mt-3 leading-relaxed line-clamp-5">
-                  {show.summary}
-                </p>
+              <p className="text-sm text-muted mt-3 leading-relaxed line-clamp-5">{show.summary}</p>
             )}
             <div className="mt-4 flex flex-wrap gap-2">
               {show.resume && (
@@ -1158,13 +1218,12 @@ function PlexShowView({
                   label={t("plex.series.playFromStart")}
                 />
               )}
-                <ActionBtn
-                  onClick={() => markAll(!watched)}
-                  disabled={busy}
-                  icon={watched ? CheckCheck : Check}
-                  label={
-                    watched ? t("plex.series.markShowUnwatched") : t("plex.series.markShowWatched")
-                  }
+              <WatchedToggle
+                watched={watched}
+                busy={busy}
+                onToggle={() => markAll(!watched)}
+                watchedLabel={t("plex.series.markShowUnwatched")}
+                unwatchedLabel={t("plex.series.markShowWatched")}
               />
               {allKeys.length > 0 && (
                 <ActionBtn
@@ -1183,8 +1242,7 @@ function PlexShowView({
                 />
               )}
             </div>
-            </div>
-          </div>
+          </DetailHero>
 
           {/* Seasons — in a glassy panel like the movie info-page strips. */}
           <section
@@ -1296,8 +1354,14 @@ function PlexSeasonView({
         <LoadingState label={t("plex.loading")} />
       ) : (
         <>
-          <div className="glass relative rounded-2xl p-4 sm:p-5 mb-8 flex gap-4 sm:gap-5">
-            <div className="absolute right-3 top-3 z-base">
+          <DetailHero
+            thumb={se.thumb}
+            posterTitle={se.status === "new" ? t("plex.play") : t("plex.resume")}
+            posterDisabled={!se.resume}
+            showPlayOverlay={!!se.resume}
+            onPosterClick={() => se.resume && onPlay(se.resume.id, allKeys)}
+            posterSizeClass="w-28 sm:w-40"
+            customizeMenu={
               <DetailCustomizeMenu
                 artBg={artBg}
                 onToggleArtBg={toggleArtBg}
@@ -1305,25 +1369,8 @@ function PlexSeasonView({
                 onToggleCast={toggleCast}
                 hasCast={false}
               />
-            </div>
-            <button
-              onClick={() => se.resume && onPlay(se.resume.id, allKeys)}
-              disabled={!se.resume}
-              className="group/poster relative w-28 sm:w-40 shrink-0 self-start"
-              title={se.status === "new" ? t("plex.play") : t("plex.resume")}
+            }
           >
-              <img
-                src={se.thumb}
-                alt=""
-                className="w-full aspect-2/3 object-cover rounded-xl border border-border"
-              />
-              {se.resume && (
-                <div className="absolute inset-0 rounded-xl bg-black/40 opacity-0 group-hover/poster:opacity-100 transition grid place-items-center">
-                  <Play className="w-10 h-10 text-white" fill="currentColor" />
-                </div>
-              )}
-            </button>
-            <div className="min-w-0 flex-1">
             <button
               onClick={onBack}
               className="text-sm text-muted hover:text-accent transition text-left"
@@ -1351,15 +1398,12 @@ function PlexSeasonView({
                   label={t("plex.series.playFromStart")}
                 />
               )}
-                <ActionBtn
-                  onClick={() => markAll(!watched)}
-                  disabled={busy}
-                  icon={watched ? CheckCheck : Check}
-                  label={
-                    watched
-                      ? t("plex.series.markSeasonUnwatched")
-                      : t("plex.series.markSeasonWatched")
-                  }
+              <WatchedToggle
+                watched={watched}
+                busy={busy}
+                onToggle={() => markAll(!watched)}
+                watchedLabel={t("plex.series.markSeasonUnwatched")}
+                unwatchedLabel={t("plex.series.markSeasonWatched")}
               />
               {seasonKeys.length > 0 && (
                 <ActionBtn
@@ -1375,8 +1419,7 @@ function PlexSeasonView({
                 />
               )}
             </div>
-            </div>
-          </div>
+          </DetailHero>
 
           <div className="grid grid-cols-[repeat(auto-fill,minmax(230px,1fr))] gap-x-3 gap-y-4">
             {se.episodes.map((ep) => (