It occurred to me as I went down the stairs to dinner that I could have shortcut the entire long explanation above with this albeit negative, observation:
When you're shown a stylized bicycle wheel and wish to discuss the trail, there are only three important details, and none of them is the shape of the fork. They are the fork rake, the radius of the inflated tyre (which isn't mentioned above but also increases trail proportionately) and the head tube angle.
Or, without knowing the shape of the fork, you can take three points from tyre circumference, axle centre offset and head tube angle and by plotting them from axle level mathematically or geometrically determine the trail at ground level. Designers use this process in reverse from desired trail to arrive at the steering axis inclination, which they then devide between head angle and fork rake according to the tubes they have or can get.
Thus, in this illustration from http://cyclingabout.com/understanding-bicycle-frame-geometry/ —
(https://cyclingabout.com/wp-content/uploads/2013/10/wpid-Photo-4-Oct-2013-1246-am.jpg)
— the better short wheelbase fast touring bike, the one you want to be on after fourteen hours in the saddle with the hotel still ten miles up an Alpine cliff is the one on the left with the large trail even if the one on the right has the softer "touring fork".
The one on the right would need to have the head angle slackened considerably, so that the trail exceeds that of the lefthand illustration, to be a more stable bike. Then, because of the curve in the fork, it would also have a better ride.
The curvature of the fork may be good as a suspension element but as a trail element it comes into play (as a derived rake function) only in conjunction with head tube angle and tyre circumference.
You can never judge the stability of a bike from the shape of the fork alone.