Add Microsoft Testing Platform (MTP) integration for device testing

[mattleibow]

Summary

Adds Microsoft Testing Platform (MTP) v2 support to DeviceRunners, enabling dotnet test to work with device-targeted MAUI/Blazor test projects across Android, iOS, macCatalyst, Windows, and WASM.

This is purely additive — existing visual runners are completely untouched.

Architecture

dotnet test → MSBuild → RunCommand (DeviceRunners CLI in MTP host mode)
                              ↓
                    Deploy + Launch app on device
                              ↓
              App starts → MTP discovers/runs tests
                              ↓
              TcpStreamingConsumer → NDJSON over TCP (native)
              ConsoleStreamingConsumer → console.log via CDP (WASM)
                              ↓
              CLI receives events → maps to TestNodeUpdateMessage
                              ↓
              dotnet test shows results in real-time

New Packages

Package	Purpose
DeviceRunners.Testing.Platform	Core: builder interface, TCP/console streaming consumers, TestNodeMapper
DeviceRunners.Testing.Platform.Maui	UseTestingPlatformRunner(MauiAppBuilder) integration
DeviceRunners.Testing.Platform.Blazor	UseTestingPlatformRunner(WebAssemblyHostBuilder) integration
DeviceRunners.Testing.Platform.Xunit3	AddXunit3() — registers xunit v3 as test framework
DeviceRunners.Testing.Platform.MSTest	AddMSTest() — registers MSTest
DeviceRunners.Testing.Platform.NUnit	AddNUnit() — registers NUnit
DeviceRunners.Testing.Platform.Targets	MSBuild .props/.targets for dotnet test wiring

Consumer API (what users write)

MAUI app

var builder = MauiApp.CreateBuilder();
builder.UseMauiApp<App>();
builder.UseTestingPlatformRunner(mtp =>
{
    mtp.AddXunit3();
    mtp.AddCliConfiguration();
});
return builder.Build();

Blazor WASM app

var builder = WebAssemblyHostBuilder.CreateDefault(args);
builder.UseTestingPlatformRunner(mtp =>
{
    mtp.AddXunit3();
    mtp.AddCliConfiguration();
});
await builder.Build().RunAsync();

Key Design Decisions

• Single-assembly model — tests live in the app project (matches MTP's model, enables future AOT)
• Two transports, same NDJSON format — TCP for native, console.log+CDP for WASM
• Independent from visual runner — separate UseTestingPlatformRunner path
• Same CLI binary — --server flag branches to MTP host mode
• context.Complete() always called — host-side calls it in finally block (mandatory or dotnet test hangs)

Commits

1. Device-side packages (core, MAUI, Blazor, xunit3, MSTest, NUnit)
2. Host-side MTP bridge in CLI (ITestFramework implementation)
3. MSBuild targets fix (correct binary name)
4. MAUI sample app (MtpDeviceTests)
5. Blazor WASM sample app (MtpBrowserTests)

Build Status

• ✅ Full solution builds (0 errors, 0 warnings)
• ✅ All 149 existing tests pass
• ✅ MTP sample builds for Android, iOS, macCatalyst
• ✅ MTP Blazor sample builds for WASM