fix: prevent memory leaks in Command and Http classes (#1677)

- Command: Properly dispose CancellationTokenRegistration using 'await using'
  to ensure the registration callback is unregistered when the method exits
  (fixes #1632)

- Http: Remove incorrect disposal of HttpClient from IHttpClientFactory.
  The factory manages HttpClient lifetime, so disposing them can cause issues.
  Now properly tracks and disposes ServiceProviders for internally created
  HttpClients (fixes #1567)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: thomhurst

src/ModularPipelines/Context/Command.cs

@@ -270,7 +270,7 @@ private async Task<CommandResult> Of(CliWrap.Command command,
 
         using var forcefulCancellationToken = new CancellationTokenSource();
 
-        cancellationToken.Register(() =>
+        await using var registration = cancellationToken.Register(() =>
         {
             try
             {

src/ModularPipelines/Http/Http.cs

@@ -16,7 +16,7 @@ internal class Http : IHttp, IDisposable
     private readonly IHttpLogger _httpLogger;
     private readonly IOptions<PipelineOptions> _pipelineOptions;
 
-    private readonly ConcurrentDictionary<HttpLoggingType, HttpClient> _loggingHttpClients = new();
+    private readonly ConcurrentDictionary<HttpLoggingType, (HttpClient Client, ServiceProvider Provider)> _loggingHttpClients = new();
 
     public Http(HttpClient defaultHttpClient,
         IModuleLoggerProvider moduleLoggerProvider,
@@ -94,19 +94,24 @@ public HttpClient GetLoggingHttpClient(HttpLoggingType loggingType)
                 httpClientBuilder.AddHttpMessageHandler<StatusCodeLoggingHttpHandler>();
             }
 
-            return serviceCollection.BuildServiceProvider()
+            var serviceProvider = serviceCollection.BuildServiceProvider();
+            var httpClient = serviceProvider
                 .GetRequiredService<ModularPipelinesHttpClientProvider>()
                 .HttpClient;
-        });
+
+            return (httpClient, serviceProvider);
+        }).Client;
     }
 
     public void Dispose()
     {
-        HttpClient.Dispose();
+        // Note: HttpClient is obtained from IHttpClientFactory via DI and should NOT be disposed.
+        // The factory manages the lifetime of HttpClient instances.
 
-        foreach (var httpClient in _loggingHttpClients.Values)
+        // Dispose the ServiceProviders which will clean up their internal resources
+        foreach (var (_, provider) in _loggingHttpClients.Values)
         {
-            httpClient.Dispose();
+            provider.Dispose();
         }
     }