feat(plex): S3 toolbar relocation — scope to header, sort above the cards

Move the two "what am I browsing" controls out of the filter sidebar to where
they're always in reach, matching the Feed's layout:

- Library scope (both/movie/show) → a compact SegmentedToggle in the header next
  to the search box (new PlexScopeToggle, reads the same provider state).
- Sort → a SortControl in the row above the cards (into the PageToolbar band,
  count on the left, sort on the right), like the Feed.

Sidebar cleanup: drop the `scope` and `sort` island cards; the panel badge now
counts only the filters still in the panel (expanded filters + watch-state);
remove the now-unused sort imports. panelLayout drops both from the default plex
order (stale saved-layout keys are auto-filtered, so existing layouts degrade
cleanly). usePlexActiveFilters no longer emits a sort chip — sort is an
always-visible control now, not a removable narrowing (same as the Feed).

FE-only, no backend/migration. typecheck + eslint clean; 171 vitest green;
self-E2E verified (header scope drives the grid, sort control reorders, sidebar
no longer shows the two cards, no sort chip).

frontend/src/components/PlexScopeToggle.tsx

@@ -0,0 +1,26 @@
+import { useTranslation } from "react-i18next";
+import SegmentedToggle from "./SegmentedToggle";
+import { usePlex, usePlexActions } from "./PlexProvider";
+
+// The Plex library scope (both | movie | show) as a compact header control, sitting next to the
+// search box (S3 toolbar relocation — it used to be a sidebar island). Reads/writes the same
+// provider state the sidebar did, so scope stays in sync everywhere; reuses the shared
+// SegmentedToggle and the existing plex.filter.scopeOpt.* labels.
+const SCOPES = ["both", "movie", "show"] as const;
+
+export default function PlexScopeToggle() {
+  const { t } = useTranslation();
+  const { scope } = usePlex();
+  const { setScope } = usePlexActions();
+  return (
+    <div className="pointer-events-auto shrink-0">
+      <SegmentedToggle
+        size="md"
+        ariaLabel={t("plex.filter.scope")}
+        options={SCOPES.map((s) => ({ value: s, label: t(`plex.filter.scopeOpt.${s}`) }))}
+        value={scope}
+        onChange={setScope}
+      />
+    </div>
+  );
+}