fix(channels): address R13 S3 review findings

- ActionMenu: skip disabled items in roving keyboard nav (plumb
  disabledIndices through the AnchoredPopover platform); a pending
  action no longer strands focus on an unfocusable button.
- ActionMenu + ChannelStatsPopover: add type="button" to the popover
  triggers so they can't submit an enclosing form.
- ChannelStatsPopover: restore the per-stat explanations as a native
  title on each row — the guidance the old inline stats showed is back.
- i18n: drop the now-dead channels.tags.yourTags / .manage keys (en+hu);
  the stats *Hint keys are live again via the restored row titles.
- test: cover ActionMenu (open/select/close/disabled) and
  ChannelStatsPopover (rows, conditional ETA row, per-row hint title).

frontend/src/components/ChannelStatsPopover.tsx

@@ -29,17 +29,26 @@ export default function ChannelStatsPopover({ status }: { status: MyStatus }) {
     offset: 8,
   });
 
-  const rows: { icon: LucideIcon; label: string; value: string | number }[] = [
-    { icon: Users, label: t("channels.stats.channels"), value: status.channels_total },
+  // Each row keeps the per-stat explanation the old inline stats carried (as a native `title` on the
+  // row), so hovering a figure still tells the user what it counts — the guidance is not lost.
+  const rows: { icon: LucideIcon; label: string; value: string | number; hint: string }[] = [
+    {
+      icon: Users,
+      label: t("channels.stats.channels"),
+      value: status.channels_total,
+      hint: t("channels.stats.channelsHint"),
+    },
     {
       icon: RefreshCw,
       label: t("channels.stats.recentSynced"),
       value: `${status.channels_recent_synced}/${status.channels_total}`,
+      hint: t("channels.stats.recentSyncedHint"),
     },
     {
       icon: History,
       label: t("channels.stats.fullHistory"),
       value: `${status.channels_deep_done}/${status.channels_deep_requested}`,
+      hint: t("channels.stats.fullHistoryHint"),
     },
     ...(status.deep_pending_count > 0
       ? [
@@ -47,20 +56,28 @@ export default function ChannelStatsPopover({ status }: { status: MyStatus }) {
             icon: Clock,
             label: t("channels.stats.left"),
             value: formatEta(status.deep_eta_seconds),
+            hint: t("channels.stats.leftHint", { count: status.deep_pending_count }),
           },
         ]
       : []),
-    { icon: Film, label: t("channels.stats.myVideos"), value: status.my_videos.toLocaleString() },
+    {
+      icon: Film,
+      label: t("channels.stats.myVideos"),
+      value: status.my_videos.toLocaleString(),
+      hint: t("channels.stats.myVideosHint"),
+    },
     {
       icon: Zap,
       label: t("channels.stats.quotaLeft"),
       value: status.quota_remaining_today.toLocaleString(),
+      hint: t("channels.stats.quotaLeftHint"),
     },
   ];
 
   return (
     <>
       <button
+        type="button"
         ref={pop.refs.setReference}
         {...pop.getReferenceProps()}
         className="glass-card glass-hover inline-flex items-center gap-1.5 rounded-lg px-2.5 py-1.5 text-sm text-muted transition"
@@ -74,7 +91,11 @@ export default function ChannelStatsPopover({ status }: { status: MyStatus }) {
         className="glass-menu w-60 rounded-xl p-2 text-xs animate-[popIn_0.16s_ease]"
       >
         {rows.map((r) => (
-          <div key={r.label} className="flex items-center gap-2.5 px-1.5 py-1.5">
+          <div
+            key={r.label}
+            title={r.hint}
+            className="flex cursor-help items-center gap-2.5 px-1.5 py-1.5"
+          >
             <r.icon className="h-4 w-4 shrink-0 text-muted" aria-hidden="true" />
             <span className="flex-1 text-muted">{r.label}</span>
             <span className="tabular-nums font-medium text-fg">{r.value}</span>