Default the window zoom factor instead of passing NaN

[sadiqk2]

window/open destructures zoomFactor from an optional payload and later does:

window.webContents.on('dom-ready', () => {
    window.webContents.setZoomFactor(parseFloat(zoomFactor));
});

When the key is absent that is parseFloat(undefined) → NaN, and setZoomFactor(NaN) does not no-op — the page renders at an extreme zoom. I hit this with a window showing about four enormous letters and no other symptom.

Native\Desktop\Windows\Window declares protected float $zoomFactor = 1.0 and always serialises it, so the Laravel client never reaches this path. It only surfaces for a caller that omits the key, which the endpoint otherwise permits.

The fix falls back to 1 for anything non-finite or non-positive.

[sadiqk2]

@simonhamp kindly review