feat(design): every button on its family, the chip primitive, the lint rule (E28 S3b2)

The second half of the button sweep: the remaining hand-rolled buttons in
feature components, the design lab and the components/ui composites now
stand on Button, IconButton, Pressable, Chip or DragHandle.

- Chip + DismissibleChip (filter / token / tag / suggest / ghost, 24px
  floor, 44 on touch) replace five chip geometries; FilterChipGroup
  renders Chips; overflow lanes measure a mirror painted by chipClass.
- The Plex control row is IconButton's player rung (36, 20px glyph,
  round, overlay; 44 on touch); the YT modal bar is on the sm rung with
  pressed cycle toggles and names that survive a folded label.
- New variants: IconButton ghost-accent, danger-soft; Button warn on a
  new state-warn utility. The .btn-{tone} recipes and btnCls are gone.
- Fixed on the way: membership rows (collection editor, Plex playlist
  add) announce checked/mixed; a one-letter tag chip was 21px wide;
  descriptionLinks moved out of lib/ (it renders components).
- local/button-primitive: a raw <button>/<FocusSafeButton> outside the
  control-primitive files is a lint error (contract-tested, seen red).

frontend/src/components/Home.tsx

@@ -42,6 +42,7 @@ import { PlexPosterCard } from "./plexCards";
 import { useNavigationActions } from "./navigationContext";
 import { usePlexActions } from "./plexContext";
 import { navItemAttrs } from "../lib/listNav";
+import { Pressable } from "./ui/Pressable";
 
 // The Home surface (E24) — "Mit nézzek most?".
 //
@@ -244,8 +245,7 @@ function ShelfTile({
       ? t("home.shelf.unwatchedCount", { count: count ?? 0 })
       : t("home.shelf.itemCount", { count: count ?? 0 });
   return (
-    <button
-      type="button"
+    <Pressable
       onClick={() => card.next && onPlay(card)}
       {...menuProps?.(card)}
       {...(navIndex !== undefined && navItemAttrs(navIndex))}
@@ -257,7 +257,7 @@ function ShelfTile({
       // Shift+F10, the only keyboard route to the menu. Inert to the click (the handler guards),
       // alive to all three input paths.
       aria-disabled={!card.next}
-      className="block w-full text-left rounded-xl overflow-hidden border border-border bg-surface transition-colors aria-disabled:opacity-60 [&:not([aria-disabled='true'])]:hover:border-accent"
+      className="block w-full rounded-xl overflow-hidden border border-border bg-surface transition-colors aria-disabled:opacity-60 [&:not([aria-disabled='true'])]:hover:border-accent"
     >
       <span className="block aspect-video bg-card overflow-hidden">
         {card.thumb ? (
@@ -268,7 +268,7 @@ function ShelfTile({
         <span className="block text-xs font-medium truncate">{card.title}</span>
         <span className="block text-2xs text-muted">{countLabel}</span>
       </span>
-    </button>
+    </Pressable>
   );
 }
 
@@ -307,8 +307,7 @@ function Hero({
       {...pinMenu.triggerProps(card)}
       className="mb-6 rounded-xl border border-border bg-surface p-4 grid gap-4 sm:grid-cols-[minmax(0,18rem)_1fr]"
     >
-      <button
-        type="button"
+      <Pressable
         onClick={() => onPlay(card)}
         className={`relative block w-full overflow-hidden rounded-lg border border-border bg-card ${
           card.aspect === "poster" ? "aspect-[2/3] max-w-[12rem]" : "aspect-video"
@@ -331,7 +330,7 @@ function Hero({
             />
           </span>
         ) : null}
-      </button>
+      </Pressable>
 
       <div className="flex min-w-0 flex-col">
         <p className="text-2xs font-semibold uppercase tracking-wider text-accent">{kicker}</p>