Surface workspace changes from agent panes (#3682)

* feat(app): refine workspace pane actions

Prioritize Changes when available, keep Files useful before a selection, and reserve desktop diff clicks for selection so comments require the explicit affordance. Move the Changes shortcut to Shift+G to avoid consuming a likely copy variant.

* feat(app): improve access to workspace changes

packages/app/src/panels/agent-tracks.tsx

@@ -1,4 +1,6 @@
 import { memo, useCallback, type ReactElement } from "react";
+import { WorkspaceDiffStatPill } from "@/composer/diff-stat-pill";
+import { useWorkspaceHasDiffStat } from "@/composer/workspace-diff-stat";
 import { AgentTaskList } from "@/composer/task-list";
 import { ComposerTrackBar } from "@/composer/tracks";
 import { supportsDesktopPaneSplits, useIsCompactFormFactor } from "@/constants/layout";
@@ -18,26 +20,29 @@ import { buildWorkspaceTabPersistenceKey } from "@/workspace-tabs/model";
 import { openSupportingTab } from "@/workspace-tabs/side-panel";
 
 /**
- * The pane's trackers — its subagents and its task list — as a row of pills above the composer.
+ * The pane's ambient context — workspace changes, subagents, and tasks — as a row of pills above
+ * the composer.
  *
  * The row shares the composer's keyboard transform and owns the space between itself and the
- * transcript. Its data remains agent state: a subagent row opens a tab and the task list reads
- * the agent's stream.
+ * transcript. Each pill owns its action while tab placement stays behind the workspace boundary.
  */
 export const AgentTracks = memo(function AgentTracks({
   serverId,
+  workspaceId,
   subagentRows,
   tasks,
   archiveFinishedStatus,
   onArchiveFinished,
 }: {
   serverId: string;
+  workspaceId: string;
   subagentRows: SubagentRow[];
   tasks: TodoEntry[] | undefined;
   archiveFinishedStatus: ArchiveFinishedStatus;
   onArchiveFinished: () => void;
 }): ReactElement | null {
-  const { workspaceId, tabId, openTab } = usePaneContext();
+  const { tabId, openTab } = usePaneContext();
+  const hasWorkspaceDiffStat = useWorkspaceHasDiffStat(serverId, workspaceId);
   const isCompact = useIsCompactFormFactor();
   const canSplit = supportsDesktopPaneSplits() && !isCompact;
   const openInSidePanelByDefault = useSettings(
@@ -87,13 +92,25 @@ export const AgentTracks = memo(function AgentTracks({
     },
     [canSplit, isCompact, openInSidePanelByDefault, openTab, tabId, workspaceKey],
   );
+  const handleOpenChanges = useCallback(() => {
+    if (!workspaceKey) {
+      return;
+    }
+    openSupportingTab({
+      isCompact,
+      workspaceKey,
+      target: { kind: "working_diff" },
+      openInSidePanelByDefault,
+    });
+  }, [isCompact, openInSidePanelByDefault, workspaceKey]);
 
-  if (!hasAgentTracks({ subagentRows, tasks, archiveFinishedStatus })) {
+  if (!hasWorkspaceDiffStat && !hasAgentTracks({ subagentRows, tasks, archiveFinishedStatus })) {
     return null;
   }
 
   return (
     <ComposerTrackBar>
+      <AgentTaskList tasks={tasks} />
       <SubagentsTrack
         rows={subagentRows}
         onOpenSubagent={handleOpenSubagent}
@@ -103,7 +120,11 @@ export const AgentTracks = memo(function AgentTracks({
         archiveFinishedStatus={archiveFinishedStatus}
         onDetachSubagent={canDetachSubagents ? detachSubagent : undefined}
       />
-      <AgentTaskList tasks={tasks} />
+      <WorkspaceDiffStatPill
+        serverId={serverId}
+        workspaceId={workspaceId}
+        onPress={handleOpenChanges}
+      />
     </ComposerTrackBar>
   );
 });