Add CI workflow to build Windows-only /samples heads (Phase 2 of #509)

[adrianhall]

Summary

Follow-up to #509 (Phase 2 of the samples CI rollout). This covers the Windows-only build heads that require a windows-latest runner and were explicitly deferred out of the Phase 1 build-samples.yml workflow.

Scope

Add Windows-runner coverage for:

Sample	Project(s)	TFM(s)
WinUI3 / WPF / MAUI TodoApp	samples/todoapp/TodoApp.WinUI3/TodoApp.WinUI3.csproj	net10.0-windows10.0.19041.0
WinUI3 / WPF / MAUI TodoApp	samples/todoapp/TodoApp.WPF/TodoApp.WPF.csproj	net10.0-windows
WinUI3 / WPF / MAUI TodoApp	samples/todoapp/TodoApp.MAUI/TodoApp.MAUI.csproj	Windows TFM only (net10.0-windows10.0.19041.0), conditionally added when building on Windows — maui workload required
TodoApp tutorial	samples/todoapp-tutorial/ClientApp/ClientApp.csproj	net10.0-windows (WPF)

Additional finding (discovered while implementing Phase 1, see #509)

The Phase 1 issue's inventory table listed samples/todoapp-tutorial/todoapp.sln as a plain net10.0 sample buildable on ubuntu-latest. That's inaccurate: ClientApp in that solution is a WPF app targeting net10.0-windows. Phase 1 (build-samples-todoapp-tutorial.yml) only builds ServerApp.csproj on ubuntu-latest; ClientApp needs to be picked up here, alongside the other WPF/WinUI3/MAUI-Windows heads.

Suggested approach

• Add a windows-latest job (or reusable per-sample workflow, following the pattern established in Add CI workflow to build all /samples projects on PR #509) for each of the four projects above.
• Install the maui workload before building TodoApp.MAUI.csproj.
• Should be build-only (dotnet restore + dotnet build), consistent with Phase 1.

Related

• Add CI workflow to build all /samples projects on PR #509 — Phase 1 (ubuntu-only, no-workload samples).