Take the two review notes from #664 (#678)

Both were left by the Copilot reviewer on #664, which merged before I had read them.

SolverRegressionTest had `using PeterO.Numbers;` and never named a type from it --
the EDecimal occurrences are all property accesses on a Real, which need no using.
Removed. The library builds with TreatWarningsAsErrors, so an unused using is worth
not leaving lying about.

DivergesInMagnitude was flagged for calling Limit up to three times. The three are
distinct and the || short-circuits, so there was nothing to cache, but there was a
real waste next to it: at an infinite destination there is only one side to approach
from, so the two one-sided limits are both pointless and meaningless there. They are
now only asked for when the destination is finite.

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

Author: Rafael-SOWNet

Sources/AngouriMath/Functions/Continuous/Limits/Transformations.cs

@@ -66,9 +66,17 @@ private static bool IsInfiniteNode(Entity expr)
         /// <c>g(x) * (f(x) - 1)</c>, which is well defined from either side.
         /// </remarks>
         private static bool DivergesInMagnitude(Entity power, Variable x, Entity dest)
-            => IsInfiniteNode(power.Limit(x, dest))
-                || (IsInfiniteNode(power.Limit(x, dest, ApproachFrom.Left))
-                    && IsInfiniteNode(power.Limit(x, dest, ApproachFrom.Right)));
+        {
+            if (IsInfiniteNode(power.Limit(x, dest)))
+                return true;
+            // Only worth asking one side at a time where there are two sides to ask about.
+            // Approaching an infinite destination there is only one, so the two further
+            // limits would be wasted work and would not mean anything either.
+            if (IsInfiniteNode(dest))
+                return false;
+            return IsInfiniteNode(power.Limit(x, dest, ApproachFrom.Left))
+                && IsInfiniteNode(power.Limit(x, dest, ApproachFrom.Right));
+        }
 
         private static bool IsFiniteNode(Entity expr)
             => !IsInfiniteNode(expr) && expr != MathS.NaN;

Sources/Tests/UnitTests/Common/SolverRegressionTest.cs

@@ -7,7 +7,6 @@
 
 using AngouriMath;
 using AngouriMath.Extensions;
-using PeterO.Numbers;
 using Xunit;
 
 namespace AngouriMath.Tests.Common