Desktop (Windows): clicking an image thumbnail leaves window stuck with zoom-in cursor; all clicks ignored until renderer is killed

Environment: Claude desktop 2.9939.2.0 (MSIX), Windows 11 Pro 10.0.26200, Code tab. System CPU was at 100% load at the time.

Steps: In a Code session, click an image attachment thumbnail (the ones with cursor: zoom-in).

What happens: No preview appears. From then on, anywhere over the Claude window the cursor stays the zoom-in magnifier, and every mouse click is ignored (sidebar, buttons, composer). Mouse-wheel scrolling still works. The cursor is normal over other apps. UI Automation shows no dialog or overlay on top of the page.

Tried, did not help: Esc, Ctrl+R, minimize/restore, WM_CANCELMODE to the window, a full synthetic drag inside the window.

Only fix without quitting: kill the claude.ai renderer process (claude.exe --type=renderer). The app respawns it, sessions keep running, and the cursor and clicks work again.

Likely cause: the renderer seems stuck in a drag-in-progress state after the thumbnail mousedown. Blink ignores mouse events while a drag is in progress, but wheel scrolling still works because the compositor handles it. That matches every symptom. The main process was using 100% of one core at the time.

Related, not the same: #90213 (preview overlay has no zoom/pan), #78709 (broken thumbnail preview).