Add test for collision detection with ExcludeFromSchema

Adds test to verify that parameter name collision detection occurs
even when one of the colliding parameters is excluded from schema
generation via ExcludeFromSchema = true. This addresses reviewer
feedback about potential silent de-duplication in this scenario.

Author: Copilot

test/Libraries/Microsoft.Extensions.AI.Tests/Functions/AIFunctionFactoryTest.cs

@@ -480,6 +480,28 @@ public void AIParameterNameAttribute_DuplicateNames_Throw()
         Assert.Contains("filter", ex2.Message);
     }
 
+    [Fact]
+    public void AIParameterNameAttribute_DuplicateNames_DetectedEvenWhenExcludedFromSchema()
+    {
+        // Validates that collision detection occurs in ExpectedArgumentNames collection
+        // even when one of the colliding parameters is excluded from schema generation.
+        // This addresses the concern that collisions might go undetected when
+        // ExcludeFromSchema = true for one of the parameters.
+
+        var options = new AIFunctionFactoryOptions
+        {
+            ConfigureParameterBinding = p => p.Name == "second"
+                ? new AIFunctionFactoryOptions.ParameterBindingOptions { ExcludeFromSchema = true }
+                : default
+        };
+
+        ArgumentException ex = Assert.Throws<ArgumentException>(() => AIFunctionFactory.Create(
+            ([AIParameterName("dup")] string first, [AIParameterName("dup")] string second) => first + second,
+            options));
+        Assert.Contains("dup", ex.Message);
+        Assert.Contains("AIParameterNameAttribute", ex.Message);
+    }
+
     [Fact]
     public void AIFunctionNameAttribute_DisplayNameAttribute_StillHonoredWhenNoAIFunctionNameAttribute()
     {