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/plexCards.tsx

@@ -79,7 +79,7 @@ export function PlexPosterCard({
     <div
       className="group text-left"
       {...menuProps?.(card)}
-      {...(navIndex !== undefined && navItemAttrs(navIndex))}
+      {...(navIndex !== undefined && navItemAttrs(navIndex, card.title))}
       // content-visibility keeps off-screen posters cheap to render (smoother long-list scroll).
       style={{ contentVisibility: "auto", containIntrinsicSize: "auto 300px" } as CSSProperties}
     >
@@ -262,7 +262,10 @@ export function SeasonCard({
     ? t("plex.series.markSeasonUnwatched")
     : t("plex.series.markSeasonWatched");
   return (
-    <div className="group text-left" {...(navIndex !== undefined && navItemAttrs(navIndex))}>
+    <div
+      className="group text-left"
+      {...(navIndex !== undefined && navItemAttrs(navIndex, se.title))}
+    >
       <div
         onClick={onOpen}
         role="button"
@@ -491,7 +494,7 @@ export function EpisodeCard({
       ? Math.min(100, Math.round(((ep.position_seconds ?? 0) / ep.duration_seconds) * 100))
       : 0;
   return (
-    <div className="group" {...(navIndex !== undefined && navItemAttrs(navIndex))}>
+    <div className="group" {...(navIndex !== undefined && navItemAttrs(navIndex, ep.title))}>
       <div
         onClick={onPlay}
         role="button"