fix(keys): epic-end review round 3 — the part-way clip count shows, busy buttons keep focus, cards say their names

Targeted round over 3cd0c525's fix surfaces: 14 raised, 14 fixed.

- VideoEditor: the "only X of Y clips" toast went silent exactly on the job-cap/quota refusal it was
  written for (req had already reported the error); it now always shows. The cut list holds still while
  Create queues, and a retry continues the "(i/N)" series.
- ChannelPage: Subscribe/Unsubscribe use Button `loading`, "Load more" and ChannelDiscovery's Subscribe
  block the click with aria-disabled instead of native disabled; busy Block/Hide no longer light up on
  hover.
- listNav: an item can name itself (`navItemAttrs(i, name)`) — Plex posters, seasons, episodes, message
  rows and download rows pass their title; focus on a toast's Undo keeps the removed card's slot.
- AnchoredPopover: the hand-back only for focus-managed surfaces (a hover card no longer pulls focus
  back); the dead panel-ref check is gone.
- AccountPanel: no confirmation mail offered to the demo account; send_failed copy no longer blames
  the message for an unreachable server. Pager comment points at scrollParent.

frontend/src/lib/listNav.dom.test.tsx

@@ -511,4 +511,54 @@ describe("useListNav · leaving the list, and naming the item (deep-review E11 r
     expect(a0.hasAttribute("aria-label")).toBe(false);
     expect(screen.getByTestId("a1").getAttribute("aria-label")).toBe("title");
   });
+
+  // A Plex poster's open element is the whole card — badges, title, year, rating and summary — and a
+  // season card's holds only the hover caption "Open show": named from that text, every season was
+  // "Open show" (deep-review E11 round 3). The item's own name wins.
+  it("names a card by the name its item gives, over the text of what it opens", () => {
+    function Posters() {
+      const ref = useRef<HTMLDivElement>(null);
+      useListNav(ref, { enabled: true });
+      return (
+        <div ref={ref}>
+          <div {...navItemAttrs(0, "Season 1")} data-testid="p0">
+            <div role="button" tabIndex={0} data-nav-open="">
+              Open show
+            </div>
+          </div>
+        </div>
+      );
+    }
+    render(<Posters />);
+    press("j");
+    expect(screen.getByTestId("p0").getAttribute("aria-label")).toBe("Season 1");
+  });
+
+  // Hide a card, then Undo in the toast that put up: focus on the toast's button is not the reader
+  // leaving the list, and `j` goes on from the card put back (deep-review E11 round 3).
+  it("keeps the slot when focus went to the Undo of a toast", () => {
+    withLayout(
+      (_, n) => ({ left: 0, top: n * 100 }),
+      () => {
+        const page = (ids: number[]) => (
+          <>
+            <div data-toast-region="">
+              <button data-testid="undo">undo</button>
+            </div>
+            <Swappable ids={ids} />
+          </>
+        );
+        const { rerender } = render(page([0, 1, 2, 3]));
+        press("j");
+        press("j");
+        press("j");
+        rerender(page([0, 1, 3]));
+        act(() => screen.getByTestId("undo").focus());
+        rerender(page([0, 1, 2, 3]));
+        act(() => screen.getByTestId("undo").blur());
+        press("j");
+        expect(focused()).toBe("r2");
+      },
+    );
+  });
 });