Closing Desktop while ComfyUI is starting takes ~14 s #1651

Closing Comfy Desktop while ComfyUI is still starting takes about 14 seconds before the window goes away.

Steps

1. Launch an install on Windows.
2. Close the window (✕) about 1 s after ComfyUI starts.

Expected: Desktop stops ComfyUI and exits within a second or two.
Actual: Desktop first waits for ComfyUI to finish booting (its port to come up), and only then stops it. Measured 14.2-14.7 s with ✕ at ~1 s after spawn, and 12.4-13.2 s with ✕ 6 s after launch. The same on current main and with #1625, so this isn't new.

During that time the window looks like it won't close.

Possible direction: on quit during boot, cancel the port wait and stop the process tree right away.