Add a Blueprint Node

Recommended sequence:

1. blueprint_graph_inspect to find the target graph context.
2. blueprint_graph_palette to find the UE Action Menu entry.
3. schema_inspect for blueprint_graph_edit operation addFromPalette.
4. blueprint_graph_edit with the selected palette entry.
5. blueprint_graph_layout if the edited region needs formatting.
6. blueprint_compile after meaningful changes.

Do not guess a K2 node class when a palette entry is available.