test(installer): scaffold ClaudeDo.Installer.Tests project

tests/ClaudeDo.Installer.Tests/FakeHttpMessageHandler.cs

@@ -0,0 +1,27 @@
+using System.Net;
+using System.Net.Http;
+
+namespace ClaudeDo.Installer.Tests;
+
+internal sealed class FakeHttpMessageHandler : HttpMessageHandler
+{
+    private readonly Func<HttpRequestMessage, HttpResponseMessage> _handler;
+
+    public FakeHttpMessageHandler(Func<HttpRequestMessage, HttpResponseMessage> handler)
+    {
+        _handler = handler;
+    }
+
+    public FakeHttpMessageHandler(HttpStatusCode status, string body)
+        : this(_ => new HttpResponseMessage(status) { Content = new StringContent(body) })
+    {
+    }
+
+    public List<HttpRequestMessage> Requests { get; } = new();
+
+    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
+    {
+        Requests.Add(request);
+        return Task.FromResult(_handler(request));
+    }
+}