fix(player): a layer that opens by itself takes no history entry

The auto-skip countdown and the up-next card pushed an entry without a
user gesture (Chrome's Back button skips those), and one pushed under the
open shortcuts sheet sat above it, so Back closed the hidden layer.

frontend/src/components/PlexPlayer.session.dom.test.tsx

@@ -308,6 +308,45 @@ describe("leaving an item that was played through", () => {
     act(() => void el.dispatchEvent(new Event("ended")));
   };
 
+  // A layer the player opens BY ITSELF — the auto-skip countdown, the up-next card — takes no history
+  // entry. Chrome's Back button skips an entry pushed without a user gesture, and one pushed under an
+  // open dialog (the shortcuts sheet) sat above it, so Back closed the hidden layer, not the dialog.
+  const overlayPushes = (push: { mock: { calls: unknown[][] } }) =>
+    push.mock.calls.filter(([state]) => (state as { _ov?: number } | null)?._ov != null);
+
+  it("gives the auto-skip countdown no history entry", async () => {
+    prefs({ autoSkipIntro: true, autoSkipDelay: 5 });
+    const withIntro = {
+      ...item("A"),
+      markers: [{ type: "intro", start_s: 100, end_s: 160, final: false }],
+    } as unknown as PlexItemDetail;
+    mount({ details: { A: withIntro }, sessions: { A: () => Promise.resolve(direct("A")) } });
+    await playingAt("/media/A", 50);
+    await tick();
+    const push = vi.spyOn(window.history, "pushState");
+    await playingAt("/media/A", 110); // inside the intro: the countdown starts
+    await waitFor(() => expect(screen.getByText("plex.player.skipIntro")).toBeTruthy());
+    await tick();
+    expect(overlayPushes(push)).toEqual([]);
+  });
+
+  it("gives the up-next card no history entry", async () => {
+    prefs({ upNext: true });
+    mount({
+      details: { A: item("A"), B: item("B") },
+      sessions: { A: () => Promise.resolve(direct("A")), B: () => new Promise(() => {}) },
+      queue: ["A", "B"],
+    });
+    vi.spyOn(api, "plexSetState").mockResolvedValue(undefined as never);
+    await playingAt("/media/A", 2995);
+    await tick();
+    const push = vi.spyOn(window.history, "pushState");
+    endMedia();
+    await screen.findByText("Title B"); // the card names the next item
+    await tick();
+    expect(overlayPushes(push)).toEqual([]);
+  });
+
   it("settles it as watched when it ended, so Prev does not reopen it at its last seconds", async () => {
     prefs({ upNext: false });
     const { qc, progress } = mount({

frontend/src/components/PlexPlayer.tsx

@@ -856,9 +856,10 @@ export default function PlexPlayer({ itemId, onClose, queue, fromStart = false }
   // The ONE Back cascade for the player's own ways of saying "back": the on-screen arrow, ⌫ and
   // Escape. It peels off what is layered over the video — the auto-skip countdown, then the open
   // panel, then the stats readout — and only then leaves the player. The mouse/browser Back peels
-  // the same layers one per press, the one opened last first (each holds its own history entry, see
-  // BackClose below). The shortcuts sheet is not in it: a Modal above us, with its own Escape layer
-  // and Back-to-close.
+  // the layers the viewer OPENED one per press, the one opened last first (each holds its own history
+  // entry, see BackClose below); the ones that open by themselves have none, so Back leaves past
+  // them. The shortcuts sheet is not in it: a Modal above us, with its own Escape layer and
+  // Back-to-close. Leaving closes whatever is still up first (`useHistorySubview`'s back).
   //  - The on-screen arrow is a click on "leave", not a cancel, so it does not stop a countdown.
   //  - Escape in fullscreen leaves fullscreen (the browser's own Escape) and not the player.
   const back = useCallback(
@@ -873,7 +874,6 @@ export default function PlexPlayer({ itemId, onClose, queue, fromStart = false }
   // The mouse/browser Back closes the layer whose history entry it popped (see BackClose below).
   const closeStats = useCallback(() => setStatsOpen(false), []);
   const closeAnyPanel = useCallback(() => setPanel("none"), []);
-  const cancelSkip = useCallback(() => cancelAutoSkipRef.current(), [cancelAutoSkipRef]);
 
   // Tell the shared cheat sheet which keys are live here, and whether ⇧← / ⇧→ apply (they step
   // episodes, so they are listed only inside a series).
@@ -1225,12 +1225,14 @@ export default function PlexPlayer({ itemId, onClose, queue, fromStart = false }
         )}
       </div>
 
-      {/* Each layer over the video claims its OWN history entry while it is up, so the browser/mouse
-          Back closes the one opened last and the next Back the one under it — one shared entry was
-          spent on the first layer, and the second Back left the player with the rest still up. */}
+      {/* Each layer the viewer opens over the video claims its OWN history entry while it is up, so
+          the browser/mouse Back closes the one opened last and the next Back the one under it — one
+          shared entry was spent on the first layer, and the second Back left the player with the rest
+          still up. The auto-skip countdown and the up-next card open BY THEMSELVES and claim none:
+          Chrome's Back button skips an entry pushed without a user gesture, and one pushed while the
+          shortcuts sheet was open sat above the sheet's, so Back closed the hidden layer. */}
       {statsOpen && <BackClose onBack={closeStats} />}
-      {panel !== "none" && <BackClose onBack={closeAnyPanel} />}
-      {skipProgress != null && <BackClose onBack={cancelSkip} />}
+      {panel !== "none" && panel !== "upNext" && <BackClose onBack={closeAnyPanel} />}
 
       {/* Top bar */}
       <div