feat: Enable attribute scaffolding to an existing Entity.xml

[StepanHoudek]

I rarely need to scaffold new Entities. What I mainly need do is adding attributes, relationships etc. to existing ones.

[TomProkop]

This works and it is documented in the templates repo readme. Can you describe what happened on your side?

[zdeneksrejber]

I tried it and wasn't able to complete the operation due to #102. Majority of tooling fails on this for me in the MCP. As for the scaffolding attribute itself, for me its working as expected via CLI directly.