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/ChannelPage.tsx

@@ -38,6 +38,7 @@ import { ChannelTagsControl } from "./ChannelTags";
 import { useChannelTagActions } from "../lib/useChannelTagActions";
 import { Button } from "./ui/Button";
 import { IconButton } from "./ui/IconButton";
+import { IconLink } from "./ui/LinkButton";
 
 // A dedicated channel page: an "About"-style header (banner, avatar, stats, subscribe) over the
 // channel's videos (the catalog filtered to this channel). For an un-subscribed channel it
@@ -426,16 +427,16 @@ export default function ChannelPage({
               ]}
             />
             <div className="ml-2 flex items-center gap-2">
-              <a
+              <IconLink
                 href={ytUrl}
                 target="_blank"
                 rel="noreferrer"
-                title={t("channels.row.openOnYouTube")}
-                aria-label={t("channels.row.openOnYouTube")}
-                className="inline-flex items-center justify-center w-9 h-9 rounded-lg text-muted hover:text-fg border border-border"
+                label={t("channels.row.openOnYouTube")}
+                size="md"
+                variant="outline"
               >
-                <ExternalLink className="w-4 h-4" />
-              </a>
+                <ExternalLink />
+              </IconLink>
               {ch?.subscribed && (
                 <IconButton
                   label={t("channel.showInFeed")}