This commit consolidates scripts and categories under a unified
'Executable' concept. This simplifies the architecture and improves code
readability.
- Introduce subfolders within `src/domain` to segregate domain elements.
- Update class and interface names by removing the 'I' prefix in
alignment with new coding standards.
- Replace 'Node' with 'Executable' to clarify usage; reserve 'Node'
exclusively for the UI's tree component.
c138f74460