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/plexCards.tsx

@@ -89,7 +89,7 @@ export function PlexPosterCard({
           decoding="async"
           className="w-full h-full object-cover group-hover:scale-105 transition-transform duration-200"
         />
-        {/* Playable-cost tint (always shown — a quick "will it direct-play" cue). z-20 keeps the dot
+        {/* Playable-cost tint (always shown — a quick "will it direct-play" cue). z-menu keeps the dot
             ABOVE the full-card hover-reveal overlay below (absolute inset-0, no pointer-events-none):
             without it the overlay sits on top and swallows the cursor, so the dot's native `title`
             tooltip never fired on hover (a regression once the reveal overlay was added). */}
@@ -100,7 +100,7 @@ export function PlexPosterCard({
               <span
                 role="img"
                 aria-label={t(`plex.playable.${cls}`)}
-                className={`absolute top-1.5 left-1.5 z-20 w-2 h-2 rounded-full ring-2 ring-black/40 ${PLAYABLE_TINT[cls] ?? "bg-gray-400"}`}
+                className={`absolute top-1.5 left-1.5 z-menu w-2 h-2 rounded-full ring-2 ring-black/40 ${PLAYABLE_TINT[cls] ?? "bg-gray-400"}`}
                 title={t(`plex.playable.${cls}`)}
               />
             );
@@ -181,7 +181,7 @@ export function PlexPosterCard({
 
         {/* Quick actions (playable cards): Info + watched toggle — revealed on hover, always on touch. */}
         {isPlayable && (
-          <div className="reveal absolute right-1.5 top-1.5 z-10 flex gap-1">
+          <div className="reveal absolute right-1.5 top-1.5 z-base flex gap-1">
             <IconButton
               variant="media"
               onClick={(e) => {
@@ -206,7 +206,7 @@ export function PlexPosterCard({
         )}
 
         {pct > 0 && (
-          <div className="absolute inset-x-0 bottom-0 z-10 h-1 bg-black/40">
+          <div className="absolute inset-x-0 bottom-0 z-base h-1 bg-black/40">
             <div className="h-full bg-accent" style={{ width: `${pct}%` }} />
           </div>
         )}