fix(design): claim audit part 1 — a closing key no longer re-presses its trigger, the Switch box and name, named z-levels (E28)

- In-place editors (Playlists heading + rail rename, Plex collection + playlist rename, PriorityStepper,
  Scheduler interval): a real Enter closed the editor, returned the focus to the trigger, and the same
  keystroke's activation pressed that trigger again - re-opening the editor, or in the rail selecting
  the renamed playlist. useReturnFocus.arm(e) now cancels the key's default (type-enforced); the rail and
  Scheduler editors do the same. The earlier tests dispatched a synthetic keydown, which has no default.
- Plex playlist rename: an unchanged or empty title closes with no write, as the collection rename does.
- Switch: a 36x24 box around the track (the 24 floor), 44 on a coarse pointer; `label` is required, and
  the Plex two-way-sync switch had no name.
- z-index: numeric z-10/z-20 and a literal 40 moved onto the named layer scale; a lint rule + contract.
- The /watch file card's Download is the filled primary: the page's one action.
- Stale comments: the 1024x768 floor, the retired glass tuner.

frontend/src/components/SettingsPanel.tsx

@@ -598,7 +598,12 @@ function PlexWatchSync() {
     <Section title={t("settings.plexSync.title")}>
       <p className="text-xs text-muted leading-relaxed mb-2">{t("settings.plexSync.intro")}</p>
       <SettingRow label={t("settings.plexSync.toggle")} hint={t("settings.plexSync.toggleHint")}>
-        <Switch checked={shown} disabled={busy} onChange={(v) => !busy && toggle.mutate(v)} />
+        <Switch
+          label={t("settings.plexSync.toggle")}
+          checked={shown}
+          disabled={busy}
+          onChange={(v) => !busy && toggle.mutate(v)}
+        />
       </SettingRow>
       {busy ? (
         <div className="mt-2 flex items-center gap-2 text-xs text-muted">