Add rules-aware lookup dice rolling

src/RolemasterDb.App/Features/LookupRollResult.cs

@@ -0,0 +1,10 @@
+using System.Collections.Generic;
+
+namespace RolemasterDb.App.Features;
+
+public sealed record LookupRollResult(
+    int Total,
+    IReadOnlyList<int> Rolls)
+{
+    public bool IsOpenEnded => Rolls.Count > 1;
+}