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/design-lab/batchB.tsx

@@ -24,6 +24,7 @@ import { Btn } from "./batchA";
 import { hexContrast, hueGap } from "../lib/colorMath";
 import { Reference, Sample } from "./labKit";
 import { FADE_ABOVE_PANEL, FADE_BELOW, FADE_BELOW_PANEL, FILLED, H, LAYER } from "./labTokens";
+import { Chip } from "../components/ui/Chip";
 
 // E28 S2 · Batch B — surfaces, chrome and colour, DECIDED (owner, 2026-09-24): every recommendation,
 // except B7, where the owner combined the soft tint + edge bar with optional labels. B1 (density) and
@@ -124,8 +125,8 @@ function SchemeTile({ s, mode }: { s: SchemeDef; mode: Mode }) {
         {s.name} <span className="font-normal text-muted">· {mode}</span>
       </span>
       <div className="flex flex-wrap gap-1.5">
-        <span className="btn-primary rounded-lg px-2.5 py-1 text-xs font-medium">Save</span>
-        <span className="btn-danger rounded-lg px-2.5 py-1 text-xs font-medium">Delete</span>
+        <span className="state-filled rounded-lg px-2.5 py-1 text-xs font-medium">Save</span>
+        <span className="state-danger rounded-lg px-2.5 py-1 text-xs font-medium">Delete</span>
       </div>
       <div className="flex flex-wrap gap-1.5 text-2xs">
         <span className="chip px-2 py-0.5">Filter</span>
@@ -252,13 +253,9 @@ function WatchPage() {
           <div className="text-xs text-muted">Techno Tim</div>
         </div>
         <span className="flex gap-1.5">
-          <button
-            type="button"
-            className={clsx("pill inline-flex items-center rounded-full border font-medium", H.md)}
-            aria-pressed
-          >
-            <Repeat className="h-3.5 w-3.5" /> Repeat
-          </button>
+          <Chip size="md" pressed icon={<Repeat className="size-3.5" />} className="font-medium">
+            Repeat
+          </Chip>
           <Btn tone="glass" size="md" icon={<Download className={ico} />}>
             Download
           </Btn>