fix: chat agent message actions display

packages/client/ui-conversation/tests/chat-branch-tails.spec.tsx

@@ -177,7 +177,7 @@ describe('small branch tails', () => {
     expect(view.getByText('one-liner')).toBeTruthy()
   })
 
-  it('finalized assistant messages expose copy / branch / clock after the body; streaming omits them', () => {
+  it('finalized content messages expose copy / branch / clock; Think-only and streaming omit them', () => {
     const writeText = vi.fn().mockResolvedValue(undefined)
     Object.defineProperty(navigator, 'clipboard', {
       configurable: true,
@@ -199,6 +199,17 @@ describe('small branch tails', () => {
     expect(writeText).toHaveBeenCalledWith('answer body')
     settled.unmount()
 
+    const thinkOnly = render(
+      <AssistantMarkdown
+        blocks={[{ kind: 'reasoning', text: 'only thinking' }]}
+        streaming={false}
+        time={time}
+      />,
+    )
+    expect(thinkOnly.queryByRole('button', { name: '复制' })).toBeNull()
+    expect(thinkOnly.queryByText('14:24')).toBeNull()
+    thinkOnly.unmount()
+
     const streaming = render(
       <AssistantMarkdown blocks={[{ kind: 'text', text: 'partial' }]} streaming time={time} />,
     )