use StringComparer.OrdinalIgnoreCase as default comparer for TextPrompt

src/Spectre.Console.Tests/Unit/Prompts/TextPromptTests.cs

@@ -453,4 +453,24 @@ public Task Should_Clear_Prompt_Line_When_ClearOnFinish_Is_Enabled()
         // Then
         return Verifier.Verify(console.Output);
     }
+
+    [Theory]
+    [InlineData("yes")]
+    [InlineData("Yes")]
+    [InlineData("YES")]
+    public async Task Uses_case_insensitive_comparison_when_no_comparer_is_passed(string input)
+    {
+        // Given
+        var console = new TestConsole { EmitAnsiSequences = true, };
+        console.Input.PushTextWithEnter(input);
+
+        var prompt = new TextPrompt<string>("Was the tool helpful?")
+            .AddChoices(["Yes", "Partially", "No"]);
+
+        // When
+        var result = await console.PromptAsync(prompt);
+
+        // Then
+        result.ShouldBe("Yes");
+    }
 }

src/Spectre.Console/Prompts/TextPrompt.cs

@@ -109,7 +109,7 @@ public sealed class TextPrompt<T> : IPrompt<T>, IHasCulture
     public TextPrompt(string prompt, StringComparer? comparer = null)
     {
         _prompt = prompt ?? throw new System.ArgumentNullException(nameof(prompt));
-        _comparer = comparer;
+        _comparer = comparer ?? StringComparer.OrdinalIgnoreCase;
     }
 
     /// <summary>