fix(header): sit the sync chip with the pills, shorten its tooltip

Pinning it to the header's right edge read fine on a narrow window and stranded
it on a wide one — it's a status, but it's still part of the pill row. It now
follows the search bar.

Its tooltip was the long explanation of the counts, which is redundant next to a
popover that spells them out and overflowed the viewport from the right edge.
The chip gets the counts themselves; the explanation moves onto the popover's
counts row, where there's room for it.

frontend/src/components/Header.tsx

@@ -119,11 +119,9 @@ export default function Header({
         canNext={multiModule}
       />
       {search}
-      {/* Per-user sync status — global, not per-module, so it rides the right end of the header
-          rather than costing the nav rail a whole block. */}
-      <div className="ml-auto">
-        <SyncStatus isAdmin={me.role === "admin"} onGoToFullHistory={onGoToFullHistory} />
-      </div>
+      {/* Per-user sync status — it used to cost the nav rail a whole block. It sits with the other
+          pills rather than pinned to the far right: on a wide window that just strands it. */}
+      <SyncStatus isAdmin={me.role === "admin"} onGoToFullHistory={onGoToFullHistory} />
     </div>
   );
 }