fix(plex): the player's ⋯ and tracks lists are real menus, and every close returns the focus

They were hand-built divs: no menu roles, no arrow keys, and Escape left the
focus on <body>. Both run on the popover engine now (media-tone rows), and the
tuning panel is a labelled dialog that takes the focus and hands it back to ⋯.

frontend/src/components/PlexPlayer.session.dom.test.tsx

@@ -261,9 +261,9 @@ describe("the subtitle poll and notice", () => {
     await screen.findByText("Title A");
     fireEvent.click(screen.getByLabelText("plex.player.tracks"));
     const off = await screen.findByText("plex.player.subOff");
-    expect(off.closest("button")?.getAttribute("aria-pressed")).toBe("false");
-    const pressed = document.querySelectorAll('[aria-pressed="true"]');
-    expect([...pressed].map((b) => b.textContent)).toEqual(["English"]); // the saved subtitle
+    expect(off.closest('[role="menuitemradio"]')?.getAttribute("aria-checked")).toBe("false");
+    const checked = document.querySelectorAll('[role="menuitemradio"][aria-checked="true"]');
+    expect([...checked].map((b) => b.textContent)).toEqual(["English"]); // the saved subtitle
   });
 });