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/SavedViewsPopover.tsx

@@ -4,6 +4,8 @@ import { Bookmark, Check, Settings2 } from "lucide-react";
 import { PopoverItem, PopoverSurface } from "./ui/AnchoredPopover";
 import { closeThenAct, useAnchoredPopover } from "./ui/anchoredPopoverHooks";
 import { useSavedViews } from "./savedViewsContext";
+import { IconButton } from "./ui/IconButton";
+import { Pressable } from "./ui/Pressable";
 
 // The saved-views quick-picker. The filter-panel header's icon (and the toolbar's view chip) use it as
 // their trigger: click → a popover list of the user's saved views (apply on click, the active one
@@ -26,15 +28,26 @@ export default function SavedViewsPopover({
   const label = ariaLabel ?? t("views.saved");
   return (
     <>
-      <button
-        type="button"
-        ref={pop.refs.setReference}
-        {...pop.getReferenceProps()}
-        aria-label={label}
-        className={className ?? "shrink-0 flex text-accent transition hover:text-fg"}
-      >
-        {trigger}
-      </button>
+      {/* A caller-shaped trigger (the toolbar's view chip) is a surface; the default one a glyph. */}
+      {className ? (
+        <Pressable
+          ref={pop.refs.setReference}
+          {...pop.getReferenceProps()}
+          aria-label={label}
+          className={className}
+        >
+          {trigger}
+        </Pressable>
+      ) : (
+        <IconButton
+          variant="ghost-accent"
+          ref={pop.refs.setReference}
+          {...pop.getReferenceProps()}
+          label={label}
+        >
+          {trigger}
+        </IconButton>
+      )}
       <PopoverSurface
         popover={pop}
         ariaLabel={label}