fix(channels): a pick in the +N fold keeps the focus on its chip after the fold closes

The closing popover hands the focus back to "+N" in a microtask it queues as it unmounts, after the
chip was focused (seen in Chrome; jsdom does not show it). A second focus, queued after it, wins.

frontend/src/modules/channels/TagFilterChips.dom.test.tsx

@@ -152,12 +152,14 @@ describe("TagFilterChips focus on a toggle that moves the chip", () => {
   // React gives the focus back to it after the commit. Only a remount (row ↔ fold) or a chip that
   // leaves the list loses it.
 
-  it("out of the fold: picked in the popover, it is focused on the row", () => {
+  it("out of the fold: picked in the popover, it is focused on the row", async () => {
     fit.visible = 1;
     render(<Row start={[]} />);
     fireEvent.click(moreBtn()!);
     const inFold = named("beta");
     press(inFold);
+    // The closing popover hands the focus back to "+N" a microtask later: past that too.
+    await act(async () => {});
     const onRow = named("beta");
     expect(onRow).not.toBe(inFold);
     expect(document.activeElement).toBe(onRow);

frontend/src/modules/channels/TagFilterChips.tsx

@@ -136,13 +136,14 @@ export default function TagFilterChips({
   // closed fold, or onto the chip now in its old place when it is gone. A toggle in the open fold
   // closes it, so the focus never sits outside a popover left open. Held for the frame, since the fit
   // re-decides in layout effects after the toggle's render.
-  const follow = useRef<{ key: string; at: number } | null>(null);
+  const follow = useRef<{ key: string; at: number; closed: boolean } | null>(null);
   const foldRef = useRef<HTMLDivElement | null>(null);
   const moreRef = useRef<HTMLButtonElement | null>(null);
   const onToggled = (chipKey: string, from: HTMLElement) => {
-    follow.current = { key: chipKey, at: chips.findIndex((c) => c.key === chipKey) };
+    const closed = !!foldRef.current?.contains(from);
+    follow.current = { key: chipKey, at: chips.findIndex((c) => c.key === chipKey), closed };
     requestAnimationFrame(() => (follow.current = null));
-    if (foldRef.current?.contains(from)) setOpen(false);
+    if (closed) setOpen(false);
   };
   useLayoutEffect(() => {
     const target = follow.current;
@@ -158,6 +159,9 @@ export default function TagFilterChips({
       find(inBox(foldRef.current)) ??
       (gone ? (row[Math.min(target.at, row.length - 1)] ?? moreRef.current) : moreRef.current);
     if (el && document.activeElement !== el) el.focus();
+    // The closing popover gives the focus back to "+N" in a microtask it queued as it unmounted
+    // (seen in Chrome): this one, queued after it, has the last word.
+    if (el && target.closed) queueMicrotask(() => el.isConnected && el.focus());
   });
   const setMore = (el: HTMLButtonElement | null) => {
     moreRef.current = el;