Live Reasoning panel: corner 'X' (close) button doesn't dismiss the panel

[vbalasu]

Summary

In the expanded Live Reasoning panel, the corner X (close) button does not dismiss the panel. Clicking it does nothing; the panel only disappears when the parent "Your AI Assistant" window is closed (which unmounts it).

Steps to reproduce

1. Start a solution build and open the details to watch the live building.
2. In the Live Reasoning popup, click the X in the top corner.
3. Observe: the panel stays open. Closing the "Your AI Assistant" window does hide it.

Root cause

In app/src/demo_prompt_generator/ui/components/project/chat-panel.tsx, the expanded Live Reasoning panel's header div is the drag handle: onPointerDown={handleDragStart}, and handleDragStart calls e.preventDefault() + setPointerCapture (~lines 672–673, 699).

The sibling header buttons Minimize and Show details each defensively add onPointerDown={(e) => e.stopPropagation()} (~lines 928, 940) so the drag handler doesn't swallow their interaction. The Close (X) button (~lines 946–952) is missing this guard, so pressing X starts a drag / captures the pointer instead of firing the click, and handleClose never runs.

(The minimized-pill close button at ~lines 886–893 already has the guard and works — consistent with only the expanded-panel corner X failing.)

Suggested fix

Add the same guard to the close button so it matches its siblings:

<button
  onPointerDown={(e) => e.stopPropagation()}
  onClick={handleClose}
  ...
>

Environment

Partner-facing deployment of Solution Builder (React 19 + Vite). Reported by a beta tester.