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/components/ChannelPage.busyFocus.dom.test.tsx

@@ -1,6 +1,7 @@
 // @vitest-environment jsdom
 //
-// The channel page's Block and Hide toggles while their request runs (deep-review E11 round 2). A
+// The channel page's Block and Hide toggles (deep-review E11 round 2) and its Subscribe / Unsubscribe
+// button (round 3: the same row, missed) while their request runs. A
 // focused button that turns natively `disabled` drops the keyboard to <body> in Chrome (measured for
 // ui/Button in E11 S2), so a busy toggle blocks the click with aria-disabled instead — focusable, and
 // still pressed only once.
@@ -52,42 +53,47 @@ const CH = "UCsXVk37bltHxD1rDPwtNM8Q";
 
 describe("ChannelPage — a busy toggle keeps the keyboard", () => {
   it.each([
-    ["channel.block", "blockChannel"],
-    ["channel.hide", "updateChannel"],
-  ] as const)("%s stays focusable and fires once while its request runs", async (label, call) => {
-    vi.spyOn(api, "channelDetail").mockResolvedValue({
-      id: CH,
-      title: "LEMMiNO",
-      subscribed: true,
-      blocked: false,
-      hidden: false,
-      deep_requested: false,
-      backfill_done: true,
-      stored_videos: 10,
-    } as unknown as ChannelDetail);
-    vi.spyOn(api, "tags").mockResolvedValue([] as never);
-    const pending = vi.spyOn(api, call).mockReturnValue(new Promise(() => {}) as never);
-    render(
-      <QueryClientProvider
-        client={new QueryClient({ defaultOptions: { queries: { retry: false } } })}
-      >
-        <ChannelPage
-          channelId={CH}
-          initialName="LEMMiNO"
-          me={{ id: 1, can_write: true } as unknown as Me}
-          view="cards"
-          setView={() => {}}
-          onShowInFeed={() => {}}
-        />
-      </QueryClientProvider>,
-    );
-    const button = await screen.findByRole("button", { name: label });
-    act(() => button.focus());
-    fireEvent.click(button);
-    await waitFor(() => expect(button.getAttribute("aria-disabled")).toBe("true"));
-    expect(button.hasAttribute("disabled")).toBe(false);
-    expect(document.activeElement).toBe(button);
-    fireEvent.click(button);
-    expect(pending).toHaveBeenCalledTimes(1);
-  });
+    ["channel.block", "blockChannel", true],
+    ["channel.hide", "updateChannel", true],
+    ["channel.subscribe", "subscribeChannel", false],
+    ["channel.subscribedState", "unsubscribeChannel", true],
+  ] as const)(
+    "%s stays focusable and fires once while its request runs",
+    async (label, call, subscribed) => {
+      vi.spyOn(api, "channelDetail").mockResolvedValue({
+        id: CH,
+        title: "LEMMiNO",
+        subscribed,
+        blocked: false,
+        hidden: false,
+        deep_requested: false,
+        backfill_done: true,
+        stored_videos: 10,
+      } as unknown as ChannelDetail);
+      vi.spyOn(api, "tags").mockResolvedValue([] as never);
+      const pending = vi.spyOn(api, call).mockReturnValue(new Promise(() => {}) as never);
+      render(
+        <QueryClientProvider
+          client={new QueryClient({ defaultOptions: { queries: { retry: false } } })}
+        >
+          <ChannelPage
+            channelId={CH}
+            initialName="LEMMiNO"
+            me={{ id: 1, can_write: true } as unknown as Me}
+            view="cards"
+            setView={() => {}}
+            onShowInFeed={() => {}}
+          />
+        </QueryClientProvider>,
+      );
+      const button = await screen.findByRole("button", { name: label });
+      act(() => button.focus());
+      fireEvent.click(button);
+      await waitFor(() => expect(button.getAttribute("aria-disabled")).toBe("true"));
+      expect(button.hasAttribute("disabled")).toBe(false);
+      expect(document.activeElement).toBe(button);
+      fireEvent.click(button);
+      expect(pending).toHaveBeenCalledTimes(1);
+    },
+  );
 });