fix(a11y): chips, grips, the panel tab and Back to top keep the focus somewhere real

- F5: a chip's × pressed from the keyboard hands the focus to the next chip (else the previous one,
  else what follows) before it unmounts — in DismissibleChip, so all five chip rows get it
  (`focusNeighbour` in lib/useFocusKeeper).
- F4: a drag grip names what it lifts (`common.order.dragNamed`: panel groups, personal views);
  the two generic "Drag to reorder" keys are gone.
- F6: the side panel's edge tab is out of the Tab order while the card covers it, names its panel,
  and a keyboard pin moves the focus into the card.
- F7: Back to top is no Tab stop while hidden, and a keyboard press leaves the focus on the page.

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

@@ -9,6 +9,7 @@
 import { describe, it, expect, vi, afterEach, beforeAll } from "vitest";
 import { render, screen, fireEvent, cleanup } from "@testing-library/react";
 import { FloatingTree } from "@floating-ui/react";
+import { useState } from "react";
 
 beforeAll(() => {
   class Stub {
@@ -278,6 +279,28 @@ describe("Combobox", () => {
 // page is the fixed fallback of 10 rows; the measured page is pinned in lib/listPaging.
 // E28 review J1 + J2: a failed list said "No matches" (an error dressed as an empty result), and a
 // picker whose pick was still being written took another pick.
+// E28 review F5: a chip's × pressed from the keyboard unmounted with the focus on it — to <body>,
+// out of the picker. The focus goes to the next chip's × (else the previous one, else the field).
+describe("Combobox · removing a chip from the keyboard", () => {
+  function Harness({ initial }: { initial: string[] }) {
+    const [sel, setSel] = useState(initial);
+    return <Combobox label="Genre" options={OPTIONS} selected={sel} onChange={setSel} />;
+  }
+  const x = (name: string) =>
+    screen
+      .getAllByRole("button", { name: "common.removeNamed" })
+      .find((b) => b.closest("span")?.textContent?.includes(name))!;
+
+  it("hands the focus to the neighbour chip, then to the field", () => {
+    wrap(<Harness initial={["Drama", "Action"]} />);
+    x("Drama").focus();
+    fireEvent.click(x("Drama"), { detail: 0 });
+    expect(document.activeElement).toBe(x("Action"));
+    fireEvent.click(x("Action"), { detail: 0 });
+    expect(document.activeElement).toBe(screen.getByRole("combobox"));
+  });
+});
+
 describe("Combobox · honest states", () => {
   it("says the list failed to load, not that nothing matched", () => {
     wrap(