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/ProfileEditor.tsx

@@ -10,6 +10,7 @@ import { inputCls } from "./ui/form";
 import { Button } from "./ui/Button";
 import SegmentedToggle from "./ui/SegmentedToggle";
 import FilterSelect from "./ui/FilterSelect";
+import { IconButton } from "./ui/IconButton";
 
 const HEIGHTS = [null, 2160, 1440, 1080, 720, 480, 360];
 
@@ -129,20 +130,16 @@ export default function ProfileEditor({ onClose }: { onClose: () => void }) {
             className="flex items-center gap-2 text-sm px-3 py-1.5 rounded-lg glass-card"
           >
             <span className="flex-1 truncate">{p.name}</span>
-            <button
-              onClick={() => startEdit(p)}
-              title={t("downloads.actions.rename")}
-              className="p-1 rounded-sm hover:bg-surface text-muted hover:text-fg"
-            >
-              <Pencil className="w-3.5 h-3.5" />
-            </button>
-            <button
+            <IconButton onClick={() => startEdit(p)} label={t("downloads.actions.rename")}>
+              <Pencil />
+            </IconButton>
+            <IconButton
+              variant="danger"
               onClick={() => onDelete(p)}
-              title={t("downloads.profiles.delete")}
-              className="p-1 rounded-sm hover:bg-surface text-muted hover:text-danger"
+              label={t("downloads.profiles.delete")}
             >
-              <Trash2 className="w-3.5 h-3.5" />
-            </button>
+              <Trash2 />
+            </IconButton>
           </div>
         ))}
       </div>