fix(agent-file-preview): gate file tree by active tab

Signed-off-by: gujiaming <52187003+AtomsH4@users.noreply.github.com>

Author: AtomsH4

src/renderer/pages/agents/components/AgentRightPane/AgentRightPane.tsx

@@ -200,7 +200,8 @@ function AgentRightPaneStateProvider({
   const workspaceKey = `${workspaceId ?? ''}\0${workspacePath ?? ''}`
   const previousWorkspaceKeyRef = useRef(workspaceKey)
   const lastSelectableFileRef = useRef<string | null>(null)
-  const fileTreeModelOpen = filesEnabled !== false && fileTreeOpen && shellState.open
+  const filesTabActive = activeTab === 'files'
+  const fileTreeModelOpen = filesEnabled !== false && shellState.open && filesTabActive && fileTreeOpen
 
   // Built once here (the provider survives the Host↔Overlay maximize swap), so
   // maximize/minimize no longer remounts + rematerializes the workspace tree.

src/renderer/pages/agents/components/AgentRightPane/__tests__/AgentRightPane.test.tsx

@@ -266,6 +266,25 @@ describe('AgentRightPane', () => {
     )
   })
 
+  it('keeps the file-tree model closed when opening a non-files tab', () => {
+    render(
+      <AgentRightPane sessionId="session-a" workspacePath="/workspace" messages={[]} partsByMessageId={{}}>
+        <AgentRightPane.Shortcuts />
+        <AgentRightPane.Host />
+      </AgentRightPane>
+    )
+
+    fireEvent.click(screen.getByRole('button', { name: 'agent.right_pane.tabs.status' }))
+
+    expect(screen.getByTestId('right-pane')).toHaveAttribute('data-open', 'true')
+    expect(useArtifactFileTreeModelMock).toHaveBeenLastCalledWith(
+      expect.objectContaining({
+        treeOpen: false,
+        workspacePath: '/workspace'
+      })
+    )
+  })
+
   it('keeps the file-tree model closed when files are disabled', () => {
     render(
       <AgentRightPane