fix(keys): epic-end review round 3 — the part-way clip count shows, busy buttons keep focus, cards say their names

Targeted round over 3cd0c525's fix surfaces: 14 raised, 14 fixed.

- VideoEditor: the "only X of Y clips" toast went silent exactly on the job-cap/quota refusal it was
  written for (req had already reported the error); it now always shows. The cut list holds still while
  Create queues, and a retry continues the "(i/N)" series.
- ChannelPage: Subscribe/Unsubscribe use Button `loading`, "Load more" and ChannelDiscovery's Subscribe
  block the click with aria-disabled instead of native disabled; busy Block/Hide no longer light up on
  hover.
- listNav: an item can name itself (`navItemAttrs(i, name)`) — Plex posters, seasons, episodes, message
  rows and download rows pass their title; focus on a toast's Undo keeps the removed card's slot.
- AnchoredPopover: the hand-back only for focus-managed surfaces (a hover card no longer pulls focus
  back); the dead panel-ref check is gone.
- AccountPanel: no confirmation mail offered to the demo account; send_failed copy no longer blames
  the message for an unreachable server. Pager comment points at scrollParent.

frontend/src/components/ChannelPage.tsx

@@ -481,14 +481,16 @@ export default function ChannelPage({
                 <button
                   // Busy blocks the click, not the focus: a focused button that turns natively
                   // `disabled` drops the keyboard to <body> (the rule and its measurement: ui/Button).
+                  // Nor does a busy toggle light up on hover, as if a click would do something.
                   onClick={() => !block.isPending && block.mutate()}
                   aria-disabled={block.isPending || undefined}
+                  aria-busy={block.isPending || undefined}
                   title={ch?.blocked ? t("channel.unblock") : t("channel.block")}
                   aria-label={ch?.blocked ? t("channel.unblock") : t("channel.block")}
                   className={`inline-flex items-center justify-center w-9 h-9 rounded-lg border aria-disabled:opacity-50 transition ${
                     ch?.blocked
                       ? "border-danger text-danger"
-                      : "border-border text-muted hover:text-danger hover:border-danger"
+                      : "border-border text-muted not-aria-disabled:hover:text-danger not-aria-disabled:hover:border-danger"
                   }`}
                 >
                   <Ban className="w-4 h-4" />
@@ -501,12 +503,13 @@ export default function ChannelPage({
                 <button
                   onClick={() => !toggleHidden.isPending && toggleHidden.mutate()}
                   aria-disabled={toggleHidden.isPending || undefined}
+                  aria-busy={toggleHidden.isPending || undefined}
                   title={ch.hidden ? t("channel.hiddenHint") : t("channel.hideHint")}
                   aria-label={ch.hidden ? t("channel.unhide") : t("channel.hide")}
                   className={`inline-flex items-center justify-center w-9 h-9 rounded-lg border aria-disabled:opacity-50 transition ${
                     ch.hidden
                       ? "border-accent text-accent"
-                      : "border-border text-muted hover:text-fg hover:border-fg/40"
+                      : "border-border text-muted not-aria-disabled:hover:text-fg not-aria-disabled:hover:border-fg/40"
                   }`}
                 >
                   {ch.hidden ? <EyeOff className="w-4 h-4" /> : <Eye className="w-4 h-4" />}
@@ -518,7 +521,7 @@ export default function ChannelPage({
                   <Button
                     variant="outline"
                     onClick={onUnsubscribe}
-                    disabled={unsubscribe.isPending}
+                    loading={unsubscribe.isPending}
                     title={t("channel.unsubscribe")}
                     icon={<Check className="w-4 h-4" />}
                   >
@@ -528,7 +531,7 @@ export default function ChannelPage({
                   <Button
                     variant="outline"
                     onClick={() => subscribe.mutate()}
-                    disabled={subscribe.isPending}
+                    loading={subscribe.isPending}
                     icon={<Plus className="w-4 h-4" />}
                   >
                     {t("channel.subscribe")}
@@ -575,9 +578,11 @@ export default function ChannelPage({
             {!ch?.subscribed && nextToken && (
               <div className="flex justify-center pb-6">
                 <button
-                  onClick={() => runExplore(nextToken)}
-                  disabled={exploring}
-                  className="inline-flex items-center gap-2 px-4 py-2 rounded-lg text-sm border border-border hover:bg-surface disabled:opacity-50"
+                  // Busy blocks the click, not the focus (see Block above).
+                  onClick={() => !exploring && runExplore(nextToken)}
+                  aria-disabled={exploring || undefined}
+                  aria-busy={exploring || undefined}
+                  className="inline-flex items-center gap-2 px-4 py-2 rounded-lg text-sm border border-border not-aria-disabled:hover:bg-surface aria-disabled:opacity-50"
                 >
                   {exploring ? (
                     <Loader2 className="w-4 h-4 animate-spin" />