feat(app): lift bulk archive above the subagents list

The archive-finished action sat at the foot of the track panel with nothing
between it and the subagent rows, so it read as one more subagent.

It now sits above the list behind a divider. The pointer enters the panel from
the pill below it, so the top edge is the far end of the trip: reaching a bulk
action costs a pass over every row it affects, and it can't land under a thumb
that was aiming for the nearest subagent.

It stays a row rather than becoming a Button. The panel is a menu surface, and
a bordered control inside a list of menu items reads as a foreign object — the
divider does the separating, not the chrome.

packages/app/src/subagents/track.tsx

@@ -4,7 +4,7 @@ import { useTranslation } from "react-i18next";
 import { Archive, Unlink } from "lucide-react-native";
 import { StyleSheet, withUnistyles } from "react-native-unistyles";
 import { getProviderIcon } from "@/components/provider-icons";
-import { ComposerTrackPill, ComposerTrackRow } from "@/composer/tracks";
+import { ComposerTrackActions, ComposerTrackPill, ComposerTrackRow } from "@/composer/tracks";
 import { Tooltip, TooltipContent, TooltipTrigger } from "@/components/ui/tooltip";
 import { useIsCompactFormFactor } from "@/constants/layout";
 import { isNative } from "@/constants/platform";
@@ -82,6 +82,15 @@ export function SubagentsTrack({
       panelTitle={t("subagents.title")}
       statusBucket={pill.statusBucket}
     >
+      {showArchiveFinished && onArchiveFinished ? (
+        <ComposerTrackActions>
+          <ArchiveFinishedRow
+            status={archiveFinishedStatus}
+            disabled={isArchivingFinished}
+            onPress={onArchiveFinished}
+          />
+        </ComposerTrackActions>
+      ) : null}
       {rows.map((row) => (
         <SubagentsTrackRow
           key={row.id}
@@ -92,21 +101,13 @@ export function SubagentsTrack({
           onDetachSubagent={onDetachSubagent}
         />
       ))}
-      {showArchiveFinished && onArchiveFinished ? (
-        <ArchiveFinishedRow
-          status={archiveFinishedStatus}
-          disabled={isArchivingFinished}
-          onPress={onArchiveFinished}
-        />
-      ) : null}
     </ComposerTrackPill>
   );
 }
 
 /**
- * Bulk archive, as a row at the foot of the panel rather than an icon next to the count. The
- * pill has no header to hang an icon off, and a destructive-ish action reads better with its
- * name attached.
+ * Bulk archive, as a row above the list rather than an icon next to the count. The pill has no
+ * header to hang an icon off, and a destructive-ish action reads better with its name attached.
  */
 function ArchiveFinishedRow({
   status,