fix(ui): focus, paging and state that a key or a finger can reach

- A key landing on a side panel's tab steps into the card it peeks open, not onto the hidden tab.
- The Channels cards keep their status / pager row at the list's end while the band is folded.
- A menu row's note shows on an enabled row too: the download state under 'Download…', not a title.
- A removal chip hands the focus to its neighbour before it goes, for every caller (the feed's and
  Plex's active filters); the hidden-filter cue's own copy is gone.
- Back to a spot within a page's end spacer lands at the page's end, not its top.
- A running push / revert is tracked per list: another list's push is no longer refused unseen.

frontend/src/components/ui/PageScroller.dom.test.tsx

@@ -81,6 +81,50 @@ describe("PageScroller scroll memory", () => {
     expect(main.scrollTop).toBe(200);
   });
 
+  // Round 2 (F8): the page's very end, whose Back-to-top spacer only shows once scrolled, is out of
+  // reach when Back rebuilds the page — and the restore gave up with the page at the top.
+  it("Back to a spot within the end's spacer lands at the page's end, not its top", () => {
+    setEntry(1);
+    const { container } = render(<PageScroller scrollKey="e:k1">x</PageScroller>);
+    const main = sizedMain(container);
+    main.scrollTop = 500; // the very end, the spacer showing
+    fireEvent.scroll(main);
+    setEntry(2);
+    notifyNav();
+    Object.defineProperty(main, "scrollHeight", { configurable: true, value: 928 }); // no spacer
+    setEntry(1);
+    notifyNav();
+    expect(main.scrollTop).toBe(428);
+  });
+
+  it("a list still far short of the spot waits for it rather than settling early", () => {
+    let frames: FrameRequestCallback[] = [];
+    vi.stubGlobal("requestAnimationFrame", (cb: FrameRequestCallback) => frames.push(cb));
+    const flush = (n: number) => {
+      for (let i = 0; i < n; i++) {
+        const run = frames;
+        frames = [];
+        for (const cb of run) cb(0);
+      }
+    };
+    setEntry(1);
+    const { container } = render(<PageScroller scrollKey="e:k1">x</PageScroller>);
+    const main = sizedMain(container);
+    main.scrollTop = 450;
+    fireEvent.scroll(main);
+    setEntry(2);
+    notifyNav();
+    flush(1);
+    Object.defineProperty(main, "scrollHeight", { configurable: true, value: 600 }); // loading
+    setEntry(1);
+    notifyNav();
+    flush(20); // held still, but 350px short: no answer yet
+    expect(main.scrollTop).toBe(0);
+    Object.defineProperty(main, "scrollHeight", { configurable: true, value: 1000 }); // loaded
+    flush(1);
+    expect(main.scrollTop).toBe(450);
+  });
+
   it("restores per content key within one entry: a new key resets to top, returning restores", () => {
     setEntry(10);
     const { container, rerender } = render(<PageScroller scrollKey="e10:a">x</PageScroller>);