fix(nav): the dead-page rewrite does not restore a spent focus stamp

It spread the event's snapshot, which still carried the sfNav stamp lib/history's own listener had
just taken off the entry, so a later landing there (an overlay closing) refocused a stale item. It
now spreads the live entry (test red on the snapshot). Also: format.test's comment named a test
image that never runs vitest; it is the gate host's locale.

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

@@ -191,6 +191,19 @@ describe("NavigationProvider · Back", () => {
     expect(window.history.state).toMatchObject({ sfPage: "feed" });
     expect(window.location.search).toBe("?keep=1");
   });
+
+  // lib/history's own listener takes a spent focus stamp off the entry it lands on; the rewrite must
+  // not put it back, or the next landing there (an overlay closing) would refocus a stale item.
+  it("does not put back the focus stamp the landing spent", () => {
+    render();
+    const st = { sfPage: "messages", sfNav: { list: 0, lists: 1 } };
+    act(() => {
+      window.history.replaceState(st, "", "/?page=messages");
+      window.dispatchEvent(new PopStateEvent("popstate", { state: st }));
+    });
+    expect(window.history.state).toMatchObject({ sfPage: "feed" });
+    expect(window.history.state).not.toHaveProperty("sfNav");
+  });
 });
 
 describe("NavigationProvider · never under an open overlay", () => {