Fix VesselDistanceComparer throwing ArgumentException when vessel position is NaN

Array.Sort() requires a consistent IComparer. The original implementation
casts float subtraction to int: (int)(distA - distB). This produces
inconsistent results when any vessel's transform position contains NaN
(NaN - NaN = NaN; (int)NaN = 0 regardless of operand order), which
violates the sort contract and causes an ArgumentException from Array.Sort()
on every FixedUpdate.

Also fixes a secondary issue where very large squared distances (> int.MaxValue)
could overflow and produce incorrect ordering.

Fix: replace (int)(distA - distB) with distA.CompareTo(distB), which handles
NaN and large values correctly.

Author: Mark Kilfoil

Source/MASFlightComputerProxy.cs

@@ -259,7 +259,7 @@ public int Compare(Vessel a, Vessel b)
             {
                 float distA = Vector3.SqrMagnitude(a.GetTransform().position - vesselPosition);
                 float distB = Vector3.SqrMagnitude(b.GetTransform().position - vesselPosition);
-                return (int)(distA - distB);
+                return distA.CompareTo(distB);
             }
         }