ci: consolidate platform pipelines and test prerequisites on macOS support

MeetingAssistant.Tests/IsolatedApplicationFactory.cs

@@ -0,0 +1,25 @@
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Mvc.Testing;
+using Microsoft.AspNetCore.TestHost;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+
+namespace MeetingAssistant.Tests;
+
+public sealed class IsolatedApplicationFactory : WebApplicationFactory<Program>
+{
+    protected override void ConfigureWebHost(IWebHostBuilder builder)
+    {
+        builder.ConfigureTestServices(services =>
+        {
+            // Endpoint tests retain production composition but opt into each background activity they exercise.
+            foreach (var descriptor in services.Where(descriptor =>
+                descriptor.ServiceType == typeof(IHostedService) &&
+                (descriptor.ImplementationType?.Assembly == typeof(Program).Assembly ||
+                 descriptor.ImplementationFactory is not null)).ToArray())
+            {
+                services.Remove(descriptor);
+            }
+        });
+    }
+}