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/plexBrowseLists.tsx

@@ -12,7 +12,8 @@ import { LoadingState, StateMessage } from "./ui/QueryState";
 import PosterTile from "./PosterTile";
 import PlexLibraryPicker from "./PlexLibraryPicker";
 import NavGrid from "./ui/NavGrid";
-import { FocusSafeButton } from "./ui/FocusSafeButton";
+import { Button } from "./ui/Button";
+import { IconButton } from "./ui/IconButton";
 
 // A collection tile's sub-line: item count · total runtime (each dropped when unknown, e.g. show-only
 // collections have no movie runtime).
@@ -109,13 +110,9 @@ function NewCollectionPanel({
     <div className="glass-card mb-6 rounded-2xl p-4">
       <div className="mb-2 flex items-center justify-between gap-2">
         <h3 className="text-sm font-semibold">{t("plex.collection.newCollection")}</h3>
-        <button
-          onClick={onClose}
-          aria-label={t("common.close")}
-          className="glass-hover grid h-8 w-8 place-items-center rounded-lg"
-        >
-          <X className="h-4 w-4" />
-        </button>
+        <IconButton size="md" onClick={onClose} label={t("common.close")}>
+          <X />
+        </IconButton>
       </div>
       <input
         autoFocus
@@ -146,14 +143,15 @@ function NewCollectionPanel({
         term={term}
         enabled={nameOk}
         renderAction={(c) => (
-          <FocusSafeButton
+          <Button
+            variant="glass"
+            size="xs"
+            icon={<Check />}
             onClick={() => create(c)}
-            disabled={busy}
-            className="glass-card glass-hover inline-flex items-center gap-1 rounded-lg px-2.5 py-1 text-xs disabled:opacity-50"
+            loading={busy}
           >
-            <Check className="h-3.5 w-3.5" />
             {t("plex.collection.createWith")}
-          </FocusSafeButton>
+          </Button>
         )}
       />
     </div>
@@ -190,13 +188,9 @@ export function PlexCollectionsBrowse({ onPick }: { onPick: (id: string, title:
           className="glass-card w-full max-w-sm rounded-lg px-3 py-1.5 text-sm focus:outline-hidden focus:ring-2 focus:ring-accent/40"
         />
         {isAdmin && !creating && (
-          <button
-            onClick={() => setCreating(true)}
-            className="glass-card glass-hover inline-flex shrink-0 items-center gap-1.5 rounded-lg px-3 py-1.5 text-sm"
-          >
-            <Plus className="h-4 w-4" />
+          <Button variant="glass" size="sm" icon={<Plus />} onClick={() => setCreating(true)}>
             {t("plex.collection.newCollection")}
-          </button>
+          </Button>
         )}
       </div>
       {creating && (