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/PlexSidebar.tsx

@@ -4,7 +4,7 @@ import { usePlexCollectionTitles } from "../lib/usePlexCollectionTitles";
 import { useTranslation } from "react-i18next";
 import { plexLang } from "../i18n";
 import { useQuery, useQueryClient } from "@tanstack/react-query";
-import { ListMusic, Plus, SlidersHorizontal, X } from "lucide-react";
+import { ListMusic, Plus, SlidersHorizontal } from "lucide-react";
 import { api, plexFilterCount, type PlexFilters } from "../lib/api";
 import { notifyActionError } from "../lib/actionErrors";
 import { type PanelLayout } from "../lib/panelLayout";
@@ -20,6 +20,7 @@ import PersonalViewsModal from "./PersonalViewsModal";
 import { useSavedViews } from "./savedViewsContext";
 import { usePlex, usePlexActions } from "./plexContext";
 import { useMe } from "../lib/useMe";
+import { DismissibleChip } from "./ui/Chip";
 
 // The Plex module's left filter column — now the shared floating SidePanel with its filter groups
 // as reorderable "islands" (same system as the feed rail). Movie libraries get the full metadata
@@ -498,16 +499,13 @@ function CollectionPicker({
 function RemovableChip({ label, onRemove }: { label: string; onRemove: () => void }) {
   const { t } = useTranslation();
   return (
-    <span className="chip px-2 py-1 text-xs">
-      <span className="truncate max-w-36">{label}</span>
-      <button
-        onClick={onRemove}
-        className="hover:opacity-70"
-        aria-label={t("common.removeNamed", { name: label })}
-      >
-        <X className="w-3 h-3" />
-      </button>
-    </span>
+    <DismissibleChip
+      onDismiss={onRemove}
+      dismissLabel={t("common.removeNamed", { name: label })}
+      className="max-w-40"
+    >
+      {label}
+    </DismissibleChip>
   );
 }