fix(web): make plan transitions admission-safe

packages/client/ui-conversation/tests/input-bar.spec.tsx

@@ -12,7 +12,7 @@ afterEach(cleanup)
 
 function setup(over?: Partial<InputBarProps>) {
   const props: InputBarProps = {
-    draft: 'hello', running: false, disabled: false, error: null,
+    draft: 'hello', running: false, submitting: false, disabled: false, error: null,
     variant: 'composer',
     onDraftChange: vi.fn(), onSend: vi.fn(), onStop: vi.fn(),
     ...over,
@@ -83,6 +83,15 @@ describe('running lock and primary button', () => {
     expect(props.onSend).not.toHaveBeenCalled()
   })
 
+  it('submission locks duplicate sends only until Host admission settles', () => {
+    const { textarea, button, props } = setup({ submitting: true })
+    expect(textarea.disabled).toBe(true)
+    expect(textarea.placeholder).toBe('正在发送…')
+    expect(button.disabled).toBe(true)
+    fireEvent.click(button)
+    expect(props.onSend).not.toHaveBeenCalled()
+  })
+
   it('idle primary sends and disables on empty draft', () => {
     const { button, props } = setup()
     fireEvent.click(button)