fix(design): claim audit part 1b — whole-row switches, the field-family edge, state-layer hovers, icon links, reason-disabled controls, 24/44 targets (E28)

- F12 (owner: A): SwitchRow, the whole settings row toggles; a Config boolean toggles from its title
  and hint (a label pointed at the switch).
- F14 (owner: B): the form dropdown trigger wears the field frame (see-through, the >= 3:1 edge);
  labelled pills keep the faint edge and the accent-edge hover. DESIGN says so, with log rows.
- F6: ~15 bg-card / bg-border / opacity hovers onto the B3 state layer; a lint rule (HOVER_SWAP)
  refuses the swap, contract-tested.
- F10: bare 14px icon links onto IconLink / LinkButton; a local lint rule refuses a glyph-only <a>.
- F13: reason-disabled controls are aria-disabled (Users, Channels backfill, Discovery, Scheduler
  runs, Config tests); FocusSafeButton now swallows the click of a caller's aria-disabled; the
  Config tests say why while dirty (testDirty, HU/EN).
- F5/F11: every control measured live at 24 (mouse) and 44 (coarse) across every page; touch-target
  is a utility that wins over a caller's min-h-6; link variants carry it too; SegmentedToggle,
  Tabs, NavRail, menu rows, PriorityStepper, sliders, CheckRow, InnerInput, card links and the rest.
- F9: DismissibleChip's label reaches the chip's 24; the Combobox chips are DismissibleChips.
- F15: the "+N" / "More..." open state worded as it renders.

frontend/src/components/Playlists.tsx

@@ -71,6 +71,7 @@ import { DragHandle } from "./ui/DragHandle";
 import { Input } from "./ui/Input";
 import { CheckRow } from "./ui/NativeControls";
 import { useReturnFocus } from "./ui/useReturnFocus";
+import { IconLink } from "./ui/LinkButton";
 
 // The playlist detail is a HYBRID table (E4 S4): real sortable/filterable column headers over a
 // body that is still a drag-reorderable @dnd-kit list.
@@ -133,7 +134,7 @@ function Row({
       }}
       // transition-COLORS, not `transition` — the bare utility animates transform too, which is
       // the same lag by another route (150ms behind the pointer, on every row).
-      className="border-b border-border/50 hover:bg-card/40 transition-colors"
+      className="border-b border-border/50 state-layer transition-colors"
       {...navItemAttrs(index)}
       {...menuProps}
     >
@@ -908,16 +909,15 @@ export default function Playlists() {
                         </IconButton>
                       )}
                       {detail.yt_playlist_id && (
-                        <a
+                        <IconLink
                           href={`https://www.youtube.com/playlist?list=${detail.yt_playlist_id}`}
                           target="_blank"
                           rel="noreferrer noopener"
-                          title={t("playlists.openOnYoutube")}
-                          aria-label={t("playlists.openOnYoutube")}
-                          className="shrink-0 text-muted hover:text-accent"
+                          label={t("playlists.openOnYoutube")}
+                          className="shrink-0"
                         >
-                          <ExternalLink className="w-3.5 h-3.5" />
-                        </a>
+                          <ExternalLink />
+                        </IconLink>
                       )}
                     </>
                   )}