test(channels): cover ActionMenu keyboard-skip + stats ETA value; drop redundant disabledIndices

Deep-review follow-up on R13 S3.

- Add a roving-keyboard-nav test proving a disabled ActionMenu item is
  skipped by arrow keys, and assert the stats "left" row renders the
  formatEta value (formatEta had no coverage anywhere).
- Remove the disabledIndices plumbing from AnchoredPopover + ActionMenu:
  it was redundant. useListNavigation already skips items via their DOM
  disabled/aria-disabled attribute, and PopoverItem renders a native
  disabled button — verified against @floating-ui/react 0.27
  isListIndexDisabled and by a mutation test. Behaviour is unchanged and
  now guarded by the new test.

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

@@ -73,6 +73,43 @@ describe("ActionMenu", () => {
     expect(onSelect).not.toHaveBeenCalled();
   });
 
+  it("skips a disabled item in roving keyboard nav", () => {
+    // items[0] disabled, items[1] + items[2] enabled. Roving keyboard focus (the `tabindex=0` item,
+    // which tracks useListNavigation's activeIndex) must NEVER land on the disabled index-0 — arrowing
+    // skips straight over it. The skip comes for free: PopoverItem renders a native `disabled` button
+    // and useListNavigation reads that DOM state (no explicit disabledIndices needed). Without it,
+    // ArrowUp/Down would strand roving focus on the inert index-0 button. (floating-ui wires this on
+    // real key nav, not on open, in jsdom — so we drive it with arrow keys.)
+    renderMenu([
+      { id: "sync", label: "Sync", onSelect: vi.fn(), disabled: true },
+      { id: "backfill", label: "Backfill", onSelect: vi.fn() },
+      { id: "reset", label: "Reset", onSelect: vi.fn() },
+    ]);
+    fireEvent.click(screen.getByRole("button", { name: "Catalog actions" }));
+    const [disabled, backfill, reset] = screen.getAllByRole("menuitem", { hidden: true }) as [
+      HTMLElement,
+      HTMLElement,
+      HTMLElement,
+    ];
+    const menu = screen.getByRole("menu", { hidden: true });
+    const rover = () =>
+      [disabled, backfill, reset].find((el) => el.getAttribute("tabindex") === "0")?.textContent;
+
+    // The disabled item never becomes the roving target, whichever way we arrow.
+    fireEvent.keyDown(menu, { key: "ArrowDown" }); // skips disabled[0] -> first enabled
+    expect(rover()).toBe("Backfill");
+    expect(disabled.getAttribute("tabindex")).toBe("-1");
+
+    fireEvent.keyDown(menu, { key: "ArrowDown" });
+    expect(rover()).toBe("Reset");
+
+    fireEvent.keyDown(menu, { key: "ArrowUp" }); // back to Backfill
+    expect(rover()).toBe("Backfill");
+    fireEvent.keyDown(menu, { key: "ArrowUp" }); // wraps over disabled[0] to the last item
+    expect(rover()).toBe("Reset");
+    expect(disabled.getAttribute("tabindex")).toBe("-1"); // still never the disabled item
+  });
+
   it("honours a custom trigger node", () => {
     renderMenu([{ id: "sync", label: "Sync", onSelect: vi.fn() }]);
     cleanup();

frontend/src/components/ActionMenu.tsx

@@ -31,15 +31,10 @@ export default function ActionMenu({
   trigger?: ReactNode;
 }) {
   const [open, setOpen] = useState(false);
-  // A disabled item (a mutation already in flight) can't take DOM focus, so roving keyboard nav must
-  // SKIP it — otherwise ArrowUp/Down strands the highlight on an inert button. The platform handles it.
-  const disabledIndices = items.flatMap((it, i) => (it.disabled ? [i] : []));
-  const pop = useAnchoredPopover({
-    open,
-    onOpenChange: setOpen,
-    placement: "bottom-end",
-    disabledIndices,
-  });
+  // A disabled item (a mutation already in flight) is skipped by roving keyboard nav automatically:
+  // PopoverItem renders it as a native `disabled` button, which useListNavigation reads and never
+  // focuses. No explicit disabledIndices needed. See ActionMenu.dom.test.tsx for the guard.
+  const pop = useAnchoredPopover({ open, onOpenChange: setOpen, placement: "bottom-end" });
   return (
     <>
       <button

frontend/src/components/AnchoredPopover.tsx

@@ -91,9 +91,6 @@ export interface AnchoredPopoverOptions {
    *  lands the roving focus on it instead of the first item — the behaviour a "pick one of these
    *  modes" menu needs. Leave unset for action menus and multi-select toggle lists. */
   selectedIndex?: number | null;
-  /** Indices of items that are disabled (e.g. an action whose mutation is already in flight), so
-   *  roving keyboard nav SKIPS them instead of stranding focus on an unfocusable disabled button. */
-  disabledIndices?: number[];
 }
 
 // Internal: call sites use the inferred hook return, they don't name the type.
@@ -178,7 +175,10 @@ export function useAnchoredPopover(opts: AnchoredPopoverOptions) {
       setHoverIndex(null);
     },
     selectedIndex: opts.selectedIndex ?? null,
-    disabledIndices: opts.disabledIndices,
+    // Disabled items are skipped automatically: with no `disabledIndices`, useListNavigation reads
+    // each item's DOM `disabled`/`aria-disabled` (PopoverItem always renders native `disabled`), so a
+    // pending/inert item is never a roving target. (Verified against @floating-ui/react 0.27
+    // `isListIndexDisabled`.) No explicit index list needed.
     loop: true,
     // Focus the first item on open for BOTH click and keyboard (the default 'auto' skips pointer-opens,
     // which strands focus on the menu container — arrows then can't enter the roving list at all).

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

@@ -19,6 +19,7 @@ vi.mock("react-i18next", async (importOriginal) => {
 
 import ChannelStatsPopover from "./ChannelStatsPopover";
 import { type MyStatus } from "../lib/api";
+import { formatEta } from "../lib/format";
 
 beforeAll(() => {
   class Stub {
@@ -76,12 +77,17 @@ describe("ChannelStatsPopover", () => {
     expect(screen.getByText((1234).toLocaleString())).toBeTruthy(); // my_videos, locale-agnostic
   });
 
-  it("shows the 'left' ETA row only while a backfill is pending", () => {
+  it("shows the 'left' ETA row only while a backfill is pending, with the formatted ETA value", () => {
     open(status({ deep_pending_count: 0 }));
     expect(screen.queryByText("channels.stats.left")).toBeNull();
     cleanup();
-    open(status({ deep_pending_count: 2 }));
+    open(status({ deep_pending_count: 2, deep_eta_seconds: 120 }));
     expect(screen.getByText("channels.stats.left")).toBeTruthy();
+    // The value is the FORMATTED ETA (via formatEta), not raw seconds — asserting it guards the
+    // formatEta wiring, which is untested anywhere else. Using the same formatEta keeps this
+    // locale/impl-agnostic (expected === what the component renders).
+    expect(screen.getByText(formatEta(120))).toBeTruthy();
+    expect(screen.queryByText("120")).toBeNull(); // never the raw seconds
   });
 
   it("keeps each stat's explanation as a per-row title (hint not lost)", () => {