[Nitro CLI] Properly handle invalid --output option value

src/Nitro/CommandLine/src/CommandLine/Extensions/RootCommandExtensions.cs

@@ -21,6 +21,13 @@ public static async Task<int> ExecuteAsync(
         // Parse command
         var parseResult = rootCommand.Parse(args);
 
+        // Short-circuit on parse errors: let InvokeAsync report them and return the
+        // corresponding exit code.
+        if (parseResult.Errors.Count > 0)
+        {
+            return await parseResult.InvokeAsync(invocationConfiguration, cancellationToken);
+        }
+
         var format = parseResult.GetValue(Opt<OptionalOutputFormatOption>.Instance);
 
         if (format.HasValue)

src/Nitro/CommandLine/test/CommandLine.Tests/Commands/GlobalOptionsCommandTests.cs

@@ -0,0 +1,22 @@
+namespace ChilliCream.Nitro.CommandLine.Tests.Commands;
+
+public sealed class GlobalOptionsCommandTests(NitroCommandFixture fixture) : CommandTestBase(fixture)
+{
+    [Fact]
+    public async Task ExecuteAsync_InvalidOutputValue_ReturnsError()
+    {
+        // arrange
+        SetupNoAuthentication();
+
+        // act
+        var result = await ExecuteCommandAsync("api", "list", "--output", "wtf");
+
+        // assert
+        Assert.Equal(1, result.ExitCode);
+        result.StdErr.MatchInlineSnapshot(
+            """
+            Argument 'wtf' not recognized. Must be one of:
+            	'json'
+            """);
+    }
+}