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/AccountPanel.tsx

@@ -196,7 +196,9 @@ export default function AccountPanel({
 
             <button
               onClick={() => resend.mutate()}
-              disabled={!a.email_configured || a.email_verified || resend.isPending}
+              // The demo account's address is never confirmed, and the server refuses to mail it — as
+              // it refuses it a set-password link below (deep-review E11 round 3).
+              disabled={user.is_demo || !a.email_configured || a.email_verified || resend.isPending}
               className="w-full glass-card glass-hover flex items-center gap-2 px-3 py-2.5 rounded-lg text-xs disabled:opacity-45 transition"
             >
               <Send className="w-4 h-4 shrink-0" />