Relocate test project: test/yavscTests -> src/Yavsc.Org.Tests

Move the integration test project from the top-level test/ directory into
src/ alongside the projects it tests. Rename the project (and folder) to
Yavsc.Org.Tests to match .NET conventions and reflect that it tests the
Org runtime primarily.

Path changes:
- test/yavscTests/yavscTests.csproj -> src/Yavsc.Org.Tests/Yavsc.Org.Tests.csproj
- All .cs / .json / .resx files moved to their new location
- PostItViewModelTests moved out to the dedicated src/PostIt.Tests project
  (it was unrelated to Org testing)

Build adjustments:
- <ProjectReference> paths shortened (..\..\src\X -> ..\X)
- PostIt project reference removed (covered by its own test project)
- <OutputType>exe added (required by xunit.v3)
- xunit.v3.common and xunit.v3.extensibility.core added to package versions

Solution + sln:
- yavsc.sln Project Name updated to 'Yavsc.Org.Tests' and path updated
- GUID preserved so existing build configs stay valid

Static web assets:
- The CopyStaticWebAssetsManifest target was hard-coding the destination
  filename to 'testhost.staticwebassets.endpoints.json', which worked
  when the assembly was named 'yavscTests'. Now that the assembly name
  is 'Yavsc.Org.Tests', ASP.NET Core's MapStaticAssets() looks for
  'Yavsc.Org.Tests.staticwebassets.endpoints.json' (entry-assembly-based
  resolution). Use $(MSBuildProjectName) so the copy target stays
  correct under any future rename.

src/Yavsc.Org.Tests/DumpHtml.cs

@@ -0,0 +1,40 @@
+using yavscTests.ServerFixtures;
+
+namespace Yavsc.Tests
+{
+    [Collection("Yavsc Server")]
+    public class DumpHtml : IClassFixture<WebServerFixture>
+    {
+        readonly WebServerFixture _server;
+        public DumpHtml(WebServerFixture server) { _server = server; }
+
+        // FIXME [Fact]
+        [Trait("debug", "html")]
+        public void DumpHomePageHtml()
+        {
+            var settings = _server.SiteSettings;
+            var handler = new HttpClientHandler
+            {
+                ServerCertificateCustomValidationCallback = (_, _, _, _) => true,
+            };
+            var httpsUrl = _server.Addresses.FirstOrDefault(u => u.StartsWith("https:"))
+                ?? _server.Addresses.FirstOrDefault() ?? "";
+                // var httpsUrl = "https://localhost:5001" ;
+            using var client = new HttpClient(handler) { BaseAddress = new Uri(httpsUrl) };
+
+            var paths = new[] { "/Home/About", "/css/site.css", "/lib/bootstrap.quartz.min.css", "/nonexistent" };
+            var sb = new System.Text.StringBuilder();
+            sb.AppendLine($"BaseAddress = {httpsUrl}");
+            foreach (var p in paths)
+            {
+                var r = client.GetAsync(p).GetAwaiter().GetResult();
+                var b = r.Content.ReadAsStringAsync().GetAwaiter().GetResult();
+                sb.AppendLine($"GET {p} => {r.StatusCode} len={b.Length} ct={r.Content.Headers.ContentType}");
+                if (b.Length > 0 && b.Length < 500)
+                    sb.AppendLine($"  body: {b.Substring(0, Math.Min(300, b.Length))}");
+            }
+
+            Assert.Fail(sb.ToString());
+        }
+    }
+}