feat(plex): move the Discover/Browse toggle into the header

The Discover ⟷ Browse switch now sits in the header next to the library-scope
pill (All / Movies / Shows), instead of on the chip row / atop the Discover
surface.

It's driven through a small one-way PlexViewBridge: PlexBrowse still OWNS the
sub-view (useHistorySubview) and publishes its top-level view + opener to the
bridge; the always-mounted Header reads it to render PlexViewToggle. A global
sub-view provider was deliberately avoided — PlexBrowse's hook remounts on every
plex entry and re-seeds from history (a page switch clears ?v + drops _sub), so
each entry starts at the Discover root; lifting it out would let the view go
stale across navigation. The toggle hides on deeper views (show/info/person/…)
and on non-plex pages (bridge cleared on unmount). sortView is just SortControl
now; the grid toolbar no longer carries the toggle.

Verified: toggle in the header, switches discover⟷grid, hides on info + on Feed,
and Feed→Plex resets to Discover (no stale view); no console errors.

frontend/src/components/PlexBrowse.tsx

@@ -25,7 +25,6 @@ import { useHistorySubview } from "../lib/history";
 import { PLEX_SUB_URL, type Sub } from "./plexSubUrl";
 import { toggleWatchState } from "../lib/plexWatch";
 import SortControl from "./SortControl";
-import SegmentedToggle from "./SegmentedToggle";
 import FilterSelect from "./FilterSelect";
 import PlexDiscover from "./PlexDiscover";
 import { PageToolbar } from "./PageShell";
@@ -34,6 +33,7 @@ import ItemCount from "./ItemCount";
 import { StateMessage } from "./QueryState";
 import { usePlexActiveFilters, usePlexClearFilters } from "./usePlexActiveFilters";
 import { usePlex, usePlexActions } from "./PlexProvider";
+import { usePublishPlexView } from "./PlexViewBridge";
 import { EpisodeCard, PlexPosterCard } from "./plexCards";
 import { PlexInfoView, PlexPersonView, PlexSeasonView, PlexShowView } from "./plexViews";
 
@@ -82,6 +82,20 @@ export default function PlexBrowse() {
   // or an added filter is a browse intent → flip to the grid (below); an explicit toggle returns.
   const sub = useHistorySubview<Sub>({ kind: "discover" }, PLEX_SUB_URL);
 
+  // Publish the top-level view (discover vs grid) + opener to the header's Discover/Browse toggle via
+  // the bridge; clear it on unmount so the toggle disappears when you leave the plex page. Keyed on the
+  // view KIND (open is behaviourally stable — it takes the next view as an arg, closing over nothing).
+  const publishView = usePublishPlexView();
+  useLayoutEffect(() => {
+    publishView({
+      isDiscover: sub.view.kind === "discover",
+      toggleable: sub.view.kind === "discover" || sub.view.kind === "grid",
+      open: sub.open,
+    });
+    return () => publishView(null);
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [sub.view.kind]);
+
   // Sidebar asked to open a playlist → push it as a subview (browser Back returns to the grid), then
   // clear the signal so it doesn't re-open.
   useEffect(() => {
@@ -366,42 +380,23 @@ export default function PlexBrowse() {
     );
   }
 
-  // Discover ⟷ Browse switch, shown on both surfaces so either can return to the other.
-  const viewToggle = (
-    <SegmentedToggle
-      size="md"
-      ariaLabel={t("plex.view.label")}
-      options={[
-        { value: "discover", label: t("plex.discover.tab") },
-        { value: "grid", label: t("plex.view.browse") },
-      ]}
-      value={sub.view.kind === "discover" ? "discover" : "grid"}
-      onChange={(v) => sub.open(v === "discover" ? { kind: "discover" } : { kind: "grid" })}
-    />
-  );
-
-  // Sort + the Discover/Browse toggle are tightly bound to the grid below, so on the grid view they
-  // live pinned to the right of the applied-filter chip row (directly above the cards), not on their
-  // own toolbar line — the same idiom as the Feed's `sortView`.
+  // Sort is tightly bound to the grid below, so on the grid view it lives pinned to the right of the
+  // applied-filter chip row (directly above the cards), not on its own toolbar line — the same idiom as
+  // the Feed's `sortView`. The Discover/Browse toggle moved up to the header (next to the scope pill).
   const sortView = (
-    <>
-      <SortControl
-        options={sortOptions}
-        sort={sortState}
-        onChange={(next) => setSort(next ?? PLEX_SORT_FALLBACK)}
-        label={t("plex.filter.sort")}
-        ascLabel={t("plex.filter.dir.asc")}
-        descLabel={t("plex.filter.dir.desc")}
-      />
-      <span className="mx-0.5 h-5 w-px bg-border" aria-hidden="true" />
-      {viewToggle}
-    </>
+    <SortControl
+      options={sortOptions}
+      sort={sortState}
+      onChange={(next) => setSort(next ?? PLEX_SORT_FALLBACK)}
+      label={t("plex.filter.sort")}
+      ascLabel={t("plex.filter.dir.asc")}
+      descLabel={t("plex.filter.dir.desc")}
+    />
   );
 
   if (sub.view.kind === "discover") {
     return (
       <div className="p-4 max-w-[1600px] mx-auto">
-        <div className="mb-4 flex items-center">{viewToggle}</div>
         <PlexDiscover
           scope={scope}
           onOpenCard={onCard}