feat(app): give composer track pills a segment per state

A mixed fan-out used to collapse the pill to its single most urgent
state, so a red dot beside "1 failed" over a child that was still
working read as the whole fan-out having stopped. Every state present
now gets its own mark and count, in the sidebar's status-group order.

packages/app/src/subagents/track.tsx

@@ -78,9 +78,9 @@ export function SubagentsTrack({
   return (
     <ComposerTrackPill
       testID="subagents-track-header"
-      label={pill.label}
+      segments={pill.segments}
+      accessibilityLabel={pill.accessibilityLabel}
       panelTitle={t("subagents.title")}
-      statusBucket={pill.statusBucket}
     >
       {showArchiveFinished && onArchiveFinished ? (
         <ComposerTrackActions divided={rows.length > 0}>