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/SearchBar.tsx

@@ -8,8 +8,9 @@ import {
 import { useTranslation } from "react-i18next";
 import { Search, X } from "lucide-react";
 import { useSearchFocusKey } from "../lib/keymap";
-import { FocusSafeButton } from "./ui/FocusSafeButton";
 import { PaletteKeycap } from "./PaletteLauncher";
+import { Button } from "./ui/Button";
+import { IconButton } from "./ui/IconButton";
 
 // The floating search pill in the top header. One component for every module that searches
 // (feed, Plex, channels, playlists): a glass rounded box with a search icon, the input, a
@@ -92,28 +93,23 @@ export default function SearchBar({
           className="flex-1 min-w-0 bg-transparent outline-hidden text-sm placeholder:text-muted"
         />
         {value && (
-          <button
-            onClick={() => onChange("")}
-            title={t("header.clearSearch")}
-            aria-label={t("header.clearSearch")}
-            className="shrink-0 p-0.5 rounded-full text-muted transition hover:text-fg hover:bg-border/60"
-          >
-            <X className="w-4 h-4" />
-          </button>
+          <IconButton onClick={() => onChange("")} label={t("header.clearSearch")}>
+            <X />
+          </IconButton>
         )}
         <PaletteKeycap />
         {onGo && (
-          <FocusSafeButton
+          <Button
+            size="sm"
             onClick={fire}
             disabled={goDisabled}
             title={goTitle ?? goLabel ?? t("header.goTip")}
-            className="shrink-0 inline-flex items-center gap-1.5 rounded-xl bg-accent px-3 py-1.5 text-xs font-semibold text-accent-fg transition hover:opacity-90 disabled:opacity-40 disabled:pointer-events-none"
           >
             {goIcon}
             <span className={goIcon ? "hidden md:inline" : undefined}>
               {goLabel ?? t("header.go")}
             </span>
-          </FocusSafeButton>
+          </Button>
         )}
       </div>
       {below}