Show Send beside Stop for desktop follow-ups · #11336

A running desktop composer now shows Send beside Stop when it has sendable content. Clearing the draft leaves Stop only. The existing submit path and disabled state are retained, and responsive web behavior remains available.

Native Electron UI with a simulated running turn confirms the base hides Send while the fix shows it. Clearing/restoring text reverses the action state; idle shows Send only. A click reaches a captured form submit event, intercepted before any provider request. A 390px responsive viewport retains Stop and Send. Web typecheck and seven existing component checks pass. Scoped lint exactly matches 35 base warnings. CI, Macroscope correctness and CodeRabbit status pass; no inline findings.

No merge. Macroscope requires human review of the changed desktop default. Fable refinement pending after the final authorized retry failed. Stacked on #11298. Images and video are captured; GitHub asset upload is pending because its background browser connection is unavailable. Native mobile is unchanged.

Before

After

Clearing and restoring the draft