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/plexViews.tsx

@@ -27,6 +27,8 @@ import PlexPlaylistAdd, { type PlexAddTarget } from "./PlexPlaylistAdd";
 import PlexCollectionEditor from "./PlexCollectionEditor";
 import { LoadingState, StateMessage } from "./ui/QueryState";
 import NavGrid from "./ui/NavGrid";
+import { Chip } from "./ui/Chip";
+import { Pressable } from "./ui/Pressable";
 
 // The Plex sub-router's view branches, split out of PlexBrowse. Each is invoked by PlexBrowse with
 // shell callbacks as props (onBack/onPlay/onFilter/…) — no view reaches back into the shell's state,
@@ -222,12 +224,9 @@ export function PlexPersonView({
                     </p>
                   )}
                 </div>
-                <button
-                  onClick={() => onFilter({ actors: [d.name] })}
-                  className="rounded-full border border-border bg-card px-3 py-1 text-xs font-medium transition hover:border-accent hover:text-accent"
-                >
+                <Chip onClick={() => onFilter({ actors: [d.name] })} className="font-medium">
                   {t("plex.person.filterBy", { name: d.name })}
-                </button>
+                </Chip>
               </div>
             </div>
             {d.biography && (
@@ -428,7 +427,7 @@ export function PlexShowView({
                 if (!badge) return null;
                 const { score } = badge;
                 return (
-                  <button
+                  <Pressable
                     onClick={
                       onFilter ? () => onFilter({ ratingMin: Math.floor(score) }) : undefined
                     }
@@ -437,7 +436,7 @@ export function PlexShowView({
                     {/* decorative rating gold — intentionally NOT a status token */}
                     · <Star className="w-3.5 h-3.5 text-amber-400" fill="currentColor" />
                     {score.toFixed(1)}
-                  </button>
+                  </Pressable>
                 );
               })()}
             </div>
@@ -645,12 +644,9 @@ export function PlexSeasonView({
               />
             }
           >
-            <button
-              onClick={onBack}
-              className="text-sm text-muted hover:text-accent transition text-left"
-            >
+            <Button variant="link-muted" onClick={onBack} className="text-sm">
               {d.show.title}
-            </button>
+            </Button>
             <h1 className="text-2xl font-semibold leading-tight">{se.title}</h1>
             <p className="text-sm text-muted mt-1">
               {t("plex.series.episodeCount", { count: se.episode_count })}