.NET: [BREAKING] .NET: Add Workflow on-Build() Orphan Validation (#1943)

* fix: Workflow Validation

* adds orphan validation to workflow builder
* adds tests for workflow validation
* expands on the underlying reasoning why type validation is not supported

* fixup: CodeGen template

dotnet/src/Microsoft.Agents.AI.Workflows.Declarative/CodeGen/ProviderTemplate.cs

@@ -110,7 +110,8 @@ foreach (string edge in ByLine(this.Edges))
 
 }
  
-            this.Write("\n\n        // Build the workflow\n        return builder.Build();\n    }\n}\n");
+            this.Write("\n\n        // Build the workflow\n        return builder.Build(validateOrphans: fal" +
+                    "se);\n    }\n}\n");
             return this.GenerationEnvironment.ToString();
         }
     }

dotnet/src/Microsoft.Agents.AI.Workflows.Declarative/CodeGen/ProviderTemplate.tt

@@ -70,6 +70,6 @@ foreach (string edge in ByLine(this.Edges))
  #>
 
         // Build the workflow
-        return builder.Build();
+        return builder.Build(validateOrphans: false);
     }
 }