Update test coverage for tool manifest consumption - maintain backward compatibility

Co-authored-by: dsplaisted <145043+dsplaisted@users.noreply.github.com>

Author: Copilot

test/dotnet-new.IntegrationTests/TemplateDiscoveryTool.cs

@@ -15,7 +15,7 @@ public TemplateDiscoveryTool(IMessageSink messageSink)
             testOutputHelper = new SharedTestOutputHelper(messageSink);
             string home = Utilities.CreateTemporaryFolder("home");
             dotnetNewTestExecutionDir = Utilities.GetTestExecutionTempFolder();
-            string toolManifestPath = Path.Combine(dotnetNewTestExecutionDir, @".config\dotnet-tools.json");
+            string toolManifestPath = Path.Combine(dotnetNewTestExecutionDir, "dotnet-tools.json");
             if (!File.Exists(toolManifestPath))
             {
                 new DotnetNewCommand(

test/dotnet.Tests/CommandTests/Tool/Install/ToolInstallLocalCommandTests.cs

@@ -315,6 +315,26 @@ out ToolCommand restoredCommand
                                "But restore do not need to 'revert' since it just set in nuget global directory");
         }
 
+        [Fact]
+        public void WhenRunWithExistingManifestInConfigDirectoryItShouldAddToExistingManifest()
+        {
+            // Test backward compatibility: ensure tools can be added to existing manifests in .config directories
+            _fileSystem.File.Delete(_manifestFilePath);
+            var configDirectory = Path.Combine(_temporaryDirectory, ".config");
+            _fileSystem.Directory.CreateDirectory(configDirectory);
+            var configManifestPath = Path.Combine(configDirectory, "dotnet-tools.json");
+            _fileSystem.File.WriteAllText(configManifestPath, _jsonContent);
+
+            var toolInstallLocalCommand = GetDefaultTestToolInstallLocalCommand();
+
+            toolInstallLocalCommand.Execute().Should().Be(0);
+
+            // Verify the tool was added to the existing .config manifest
+            var manifestPackages = _toolManifestFinder.Find();
+            manifestPackages.Should().HaveCount(1);
+            manifestPackages.First().PackageId.Should().Be(_packageIdA);
+        }
+
         private ToolInstallLocalCommand GetDefaultTestToolInstallLocalCommand()
         {
             return new ToolInstallLocalCommand(