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/PlexSearchBox.tsx

@@ -9,6 +9,7 @@ import { api } from "../lib/api";
 import { qk } from "../lib/queryKeys";
 import { useDebounced } from "../lib/useDebounced";
 import { availablePlexFields, healPlexField, plexFieldLabelKey } from "../lib/plexSearch";
+import { Pressable } from "./ui/Pressable";
 
 // The Plex header search box: the shared SearchBar enriched with the S2 search scope-pill (a
 // GitHub-style field selector inside the box) and an instant typeahead of the top matches attached
@@ -144,17 +145,16 @@ export default function PlexSearchBox() {
               <div className="px-3 py-2 text-sm text-muted">{t("plex.loading")}</div>
             )}
             {suggestions.map((c, i) => (
-              <button
+              <Pressable
                 key={c.id}
                 id={`${listId}-opt-${i}`}
                 data-idx={i}
-                type="button"
                 role="option"
                 aria-selected={hi === i}
                 onMouseDown={(e) => e.preventDefault()} // keep input focus through the click
                 onMouseEnter={() => setHi(i)}
                 onClick={() => pick(i)}
-                className={`flex w-full items-center gap-3 rounded-xl p-1.5 text-left transition ${
+                className={`flex w-full items-center gap-3 rounded-xl p-1.5 transition ${
                   hi === i ? "bg-border/60" : "hover:bg-border/40"
                 }`}
               >
@@ -173,7 +173,7 @@ export default function PlexSearchBox() {
                 ) : (
                   <Film className="w-3.5 h-3.5 shrink-0 text-muted" aria-hidden="true" />
                 )}
-              </button>
+              </Pressable>
             ))}
           </div>
         ) : null