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/Scheduler.tsx

@@ -196,8 +196,16 @@ function JobRow({
                 aria-errormessage={valid ? undefined : rangeId}
                 onChange={(e) => setDraft(e.target.value)}
                 onKeyDown={(e) => {
-                  if (e.key === "Enter") save();
-                  if (e.key === "Escape") close();
+                  // preventDefault: close() returns the focus to the trigger before this keystroke
+                  // is done, and a real Enter's own activation would press it again (useReturnFocus).
+                  if (e.key === "Enter") {
+                    e.preventDefault();
+                    save();
+                  }
+                  if (e.key === "Escape") {
+                    e.preventDefault();
+                    close();
+                  }
                 }}
               />
               <span className="text-muted text-xs">{t("scheduler.minutes")}</span>