fix(plex): deep-review follow-ups on E6 transcode + player polish

Eight verified findings from the sprint deep-review:

- Transcode cap: _enforce_cap now counts only transcode sessions, so a
  live remux (stream-copy) stream can no longer be LRU-evicted mid-play —
  matching the config comment + the HU/EN Config hint that promise remux
  is uncapped.
- Player Back: the browser/mouse Back interceptor (BackClose) now also
  mounts for the stats overlay and up-next card, so Back closes them first
  instead of ejecting the whole player (keyboard/Esc already did).
- Honest cold-start: loadSession clears sessionIsTranscode up front, so a
  transcode->direct/remux switch no longer flashes a stale "Preparing
  stream..." during the session request.
- Stats overlay a11y: the close (X) buttons in the stats, help and info
  overlays now read as "Close"/"Bezaras" (new plex.player.close key), not
  "Back"; dropped aria-live from the per-second stat grid so a screen
  reader is not flooded with telemetry.

Tests: route-level transcode routing (transcode item -> HLS re-encode
session, remux stays copy, direct opens none); start_session threading the
preset/crf/max_height knobs + hw/preexec into the ffmpeg argv; UpNextCard
countdown auto-advance, Play-now, Cancel and the S?-E? heading fallback.

Also brings UpNextCard.tsx / plexStats.ts / plexStats.test.ts to prettier.

frontend/src/components/PlexInfo.tsx

@@ -425,7 +425,7 @@ export default function PlexInfo({
               <button
                 onClick={onClose}
                 className="shrink-0 p-1.5 rounded-lg text-white/80 hover:bg-white/15"
-                aria-label={t("plex.player.back")}
+                aria-label={t("plex.player.close")}
               >
                 <X className="w-5 h-5" />
               </button>

frontend/src/components/PlexPlayer.tsx

@@ -206,6 +206,10 @@ export default function PlexPlayer({ itemId, onClose, queue }: Props) {
       setReady(false);
       setBuffering(false);
       setLoadError(null);
+      // Clear the prior item's transcode flag up front so the cold-start overlay can't show a stale
+      // "Preparing stream…" for a not-yet-known session while the plexSession request is in flight —
+      // it's re-set honestly from the response below.
+      setSessionIsTranscode(false);
       let sess;
       try {
         // Multi-audio → request the multi-rendition session (no single `audio` ordinal); the track is
@@ -832,9 +836,13 @@ export default function PlexPlayer({ itemId, onClose, queue }: Props) {
 
       {/* While a panel/menu is open or an auto-skip countdown is running, take over the browser/mouse
           Back button (history popstate) so it closes/cancels that instead of dropping to the grid. */}
-      {(menuOpen || tracksOpen || helpOpen || infoOpen || skipProgress != null) && (
-        <BackClose onBack={backIntent} />
-      )}
+      {(menuOpen ||
+        tracksOpen ||
+        helpOpen ||
+        infoOpen ||
+        statsOpen ||
+        upNextOpen ||
+        skipProgress != null) && <BackClose onBack={backIntent} />}
 
       {/* Top bar */}
       <div
@@ -1235,7 +1243,7 @@ export default function PlexPlayer({ itemId, onClose, queue }: Props) {
               <button
                 onClick={() => setHelpOpen(false)}
                 className="p-1 rounded-lg hover:bg-white/10"
-                aria-label={t("plex.player.back")}
+                aria-label={t("plex.player.close")}
               >
                 <X className="w-5 h-5" />
               </button>

frontend/src/components/PlexStatsOverlay.tsx

@@ -109,13 +109,16 @@ export function PlexStatsOverlay({
         </span>
         <button
           onClick={onClose}
-          aria-label={t("plex.player.back")}
+          aria-label={t("plex.player.close")}
           className="rounded p-0.5 text-white/60 hover:bg-white/10 hover:text-white"
         >
           <X className="h-4 w-4" />
         </button>
       </div>
-      <dl aria-live="polite" className="grid grid-cols-[auto_1fr] gap-x-3 gap-y-1 text-2xs">
+      {/* No aria-live here: the rows re-sample every second, so a live region would make a screen
+          reader announce the changing values continuously and drown out real player announcements.
+          The overlay is a role="region" (labelled above) a user reads on demand, not a status feed. */}
+      <dl className="grid grid-cols-[auto_1fr] gap-x-3 gap-y-1 text-2xs">
         {rows.map((r) => (
           <div key={r.key} className="contents">
             <dt className="text-white/55">{t(r.labelKey)}</dt>

frontend/src/components/UpNextCard.dom.test.tsx

@@ -0,0 +1,93 @@
+// @vitest-environment jsdom
+//
+// The up-next end-card's core behaviour (E6 S4): the countdown that auto-advances at ~10s (the whole
+// point — it REPLACED the old instant jump, so a regression that fires early or never is exactly the
+// bug to guard), the "Play now"/Cancel controls, and the episode heading's null season/episode
+// fallback. i18n is key-passthrough; `../lib/api` is mocked so no network runs; the countdown uses
+// performance.now, which vitest's fake timers advance alongside setInterval.
+import { describe, it, expect, afterEach, vi } from "vitest";
+import { render, screen, fireEvent, cleanup, act } from "@testing-library/react";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+
+vi.mock("react-i18next", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("react-i18next")>();
+  return { ...actual, useTranslation: () => ({ t: (key: string) => key }) };
+});
+
+vi.mock("../lib/api", () => ({
+  api: { plexItem: vi.fn(), plexImageUrl: () => "/img" },
+}));
+
+import { UpNextCard } from "./UpNextCard";
+import { api } from "../lib/api";
+
+afterEach(() => {
+  cleanup();
+  vi.useRealTimers();
+  vi.clearAllMocks();
+});
+
+function renderCard(opts: { onAdvance?: () => void; onCancel?: () => void } = {}) {
+  const qc = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+  return render(
+    <QueryClientProvider client={qc}>
+      <UpNextCard
+        nextId="e7"
+        onAdvance={opts.onAdvance ?? vi.fn()}
+        onCancel={opts.onCancel ?? vi.fn()}
+      />
+    </QueryClientProvider>,
+  );
+}
+
+describe("UpNextCard", () => {
+  it("auto-advances after the ~10s countdown, and NOT before", () => {
+    vi.useFakeTimers();
+    // A never-resolving detail query: the heading is irrelevant here and this avoids async state
+    // updates racing the fake clock.
+    (api.plexItem as ReturnType<typeof vi.fn>).mockReturnValue(new Promise(() => {}));
+    const onAdvance = vi.fn();
+    renderCard({ onAdvance });
+
+    act(() => {
+      vi.advanceTimersByTime(9000);
+    });
+    expect(onAdvance).not.toHaveBeenCalled(); // still counting down
+
+    act(() => {
+      vi.advanceTimersByTime(1200);
+    });
+    expect(onAdvance).toHaveBeenCalledTimes(1); // crossed zero → advanced exactly once
+  });
+
+  it("'Play now' advances immediately, without waiting for the countdown", () => {
+    (api.plexItem as ReturnType<typeof vi.fn>).mockReturnValue(new Promise(() => {}));
+    const onAdvance = vi.fn();
+    renderCard({ onAdvance });
+    fireEvent.click(screen.getByRole("button", { name: /playNow/ }));
+    expect(onAdvance).toHaveBeenCalledTimes(1);
+  });
+
+  it("Cancel dismisses via onCancel and does not advance", () => {
+    (api.plexItem as ReturnType<typeof vi.fn>).mockReturnValue(new Promise(() => {}));
+    const onAdvance = vi.fn();
+    const onCancel = vi.fn();
+    renderCard({ onAdvance, onCancel });
+    fireEvent.click(screen.getByText("plex.player.upNext.cancel"));
+    expect(onCancel).toHaveBeenCalledTimes(1);
+    expect(onAdvance).not.toHaveBeenCalled();
+  });
+
+  it("an episode heading falls back to S?·E? when season/episode are null", async () => {
+    (api.plexItem as ReturnType<typeof vi.fn>).mockResolvedValue({
+      id: "e7",
+      kind: "episode",
+      show_title: "Westworld",
+      title: "The Adversary",
+      season_number: null,
+      episode_number: null,
+    });
+    renderCard();
+    expect(await screen.findByText("Westworld · S?·E?")).toBeTruthy();
+  });
+});

frontend/src/components/UpNextCard.tsx

@@ -90,7 +90,14 @@ export function UpNextCard({
           >
             <span className="relative grid h-[22px] w-[22px] flex-none place-items-center">
               <svg viewBox="0 0 24 24" className="absolute inset-0 -rotate-90">
-                <circle cx="12" cy="12" r={R} fill="none" stroke="rgba(0,0,0,0.25)" strokeWidth="2" />
+                <circle
+                  cx="12"
+                  cy="12"
+                  r={R}
+                  fill="none"
+                  stroke="rgba(0,0,0,0.25)"
+                  strokeWidth="2"
+                />
                 <circle
                   cx="12"
                   cy="12"

frontend/src/i18n/locales/en/plex.json

@@ -157,6 +157,7 @@
     "buffering": "Buffering…",
     "preparing": "Preparing stream…",
     "back": "Back",
+    "close": "Close",
     "skipIntro": "Skip intro",
     "skipCredits": "Skip credits",
     "playPause": "Play / pause (space)",

frontend/src/i18n/locales/hu/plex.json

@@ -157,6 +157,7 @@
     "buffering": "Pufferelés…",
     "preparing": "Stream előkészítése…",
     "back": "Vissza",
+    "close": "Bezárás",
     "skipIntro": "Intro átugrása",
     "skipCredits": "Stáblista átugrása",
     "playPause": "Lejátszás / szünet (szóköz)",

frontend/src/lib/plexStats.test.ts

@@ -119,7 +119,9 @@ describe("buildStatRows", () => {
   });
 
   it("shows an empty classification honestly as a dash", () => {
-    expect(buildStatRows({ ...base, playable: "" }).find((r) => r.key === "mode")?.value).toBe(DASH);
+    expect(buildStatRows({ ...base, playable: "" }).find((r) => r.key === "mode")?.value).toBe(
+      DASH,
+    );
   });
 });
 

frontend/src/lib/plexStats.ts

@@ -109,7 +109,11 @@ export function buildStatRows(s: PlexStatsInput): StatRow[] {
   const rows: StatRow[] = [
     { key: "mode", labelKey: "plex.player.stats.mode", value: fmtMode(s.playable, s.hwEncoder) },
     { key: "transport", labelKey: "plex.player.stats.transport", value: s.transport },
-    { key: "res", labelKey: "plex.player.stats.resolution", value: fmtRes(s.videoWidth, s.videoHeight) },
+    {
+      key: "res",
+      labelKey: "plex.player.stats.resolution",
+      value: fmtRes(s.videoWidth, s.videoHeight),
+    },
   ];
   if (s.transport === "hls") {
     rows.push(
@@ -118,7 +122,11 @@ export function buildStatRows(s: PlexStatsInput): StatRow[] {
         labelKey: "plex.player.stats.codec",
         value: fmtCodec(s.hlsLevel?.videoCodec, s.hlsLevel?.audioCodec),
       },
-      { key: "bitrate", labelKey: "plex.player.stats.bitrate", value: fmtBitrate(s.hlsLevel?.bitrate) },
+      {
+        key: "bitrate",
+        labelKey: "plex.player.stats.bitrate",
+        value: fmtBitrate(s.hlsLevel?.bitrate),
+      },
       { key: "level", labelKey: "plex.player.stats.level", value: fmtLevel(s.hlsLevel) },
     );
   }