[FUSE] @model directive is not mapped

[davidwengier]

See screenshot. The circled area should be classified as C# ("ErrorModel" should be blue) and there should be C# transition markers around the fully qualified name

Non-FUSE:

This was found from integration test failures, being worked around in #10959

[davidwengier]

#10959 introduces a tooling unit test that should fail when FUSE is enabled

[chsienki]

@inherits is going to have the same issue too. We need to actually track where the base / model types are coming from so we can emit them with mapping information.