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/lib/feedView.ts

@@ -23,7 +23,7 @@ export interface FeedViewSpec {
    * scan, so the stacked row keeps a cap; the one-line row doesn't need as tight a one. */
   colMaxWidth: number | null;
   /** Multi-column views only: the most columns to lay out (null = as many as fit). The UPPER end of
-   * the 1024x768..ultrawide contract (E10 S4). An auto-fill grid always settles just above `minCol`,
+   * the tablet..ultrawide contract (E10 S4; tablet portrait since E28). An auto-fill grid always settles just above `minCol`,
    * so without a cap a wider screen buys more, smaller items rather than better ones — measured at
    * 3440px, `cards` laid out 11 columns of 264px. Each cap here is set so the item tops out near
    * 1.5x its own `minCol` on a 3440px ultrawide, which keeps each view recognisably itself (a capped