Move zero-to-a-power into its own helper to keep Pow's complexity down [patch]

SonarCloud S3776 counted Pow at a cognitive complexity of 17 against a
limit of 15 once the zero-base branch gained its sign check. The branch now
calls PowOfZero, which holds that check. Behaviour is unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QK96a24CjVhUK9u1Ss2YNN

Author: claude

PreciseNumber/PreciseNumber.cs

@@ -1755,10 +1755,7 @@ public PreciseNumber Pow(PreciseNumber power)
 		}
 		else if (Significand.IsZero)
 		{
-			// Zero to a negative power is one over zero, which has no value here, as for One / Zero.
-			return power.Significand.Sign < 0
-				? throw new DivideByZeroException()
-				: Zero;
+			return PowOfZero(power);
 		}
 		else if (IsUnit)
 		{
@@ -1801,6 +1798,17 @@ public PreciseNumber Pow(PreciseNumber power)
 		return FractionalPow(this, power, significantDigits);
 	}
 
+	/// <summary>
+	/// Returns zero raised to a non-zero power.
+	/// </summary>
+	/// <param name="power">The non-zero power.</param>
+	/// <returns>Zero, for a positive <paramref name="power"/>.</returns>
+	/// <exception cref="DivideByZeroException">Thrown when <paramref name="power"/> is negative, since that is one over zero, as for <c>One / Zero</c>.</exception>
+	private static PreciseNumber PowOfZero(PreciseNumber power) =>
+		power.Significand.Sign < 0
+			? throw new DivideByZeroException()
+			: Zero;
+
 	/// <inheritdoc/>
 	public static PreciseNumber operator -(PreciseNumber value) =>
 		Negate(value);