* [fix] resolve group node execution error when connecting to external nodes
Fixed ExecutableGroupNodeChildDTO.resolveInput to properly handle connections from group node children to external nodes. The method now tries to find nodes by their full ID first (for external nodes) before falling back to the shortened ID (for internal group nodes).
Added comprehensive unit tests to prevent regression.
* [feat] Add error check for unsupported group nodes inside subgraphs
Added validation to detect when group node children are executing within subgraph contexts (execution ID has >2 segments) and provide clear error message directing users to convert to subgraphs instead.
Includes comprehensive test coverage for the new validation.
