Refactor to unify scripts/categories as Executable

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.

tests/unit/shared/Stubs/CodeChangedEventStub.ts

@@ -1,15 +1,15 @@
 import type { ICodeChangedEvent } from '@/application/Context/State/Code/Event/ICodeChangedEvent';
 import type { ICodePosition } from '@/application/Context/State/Code/Position/ICodePosition';
-import type { IScript } from '@/domain/IScript';
+import type { Script } from '@/domain/Executables/Script/Script';
 
 export class CodeChangedEventStub implements ICodeChangedEvent {
   public code: string;
 
-  public addedScripts: readonly IScript[];
+  public addedScripts: readonly Script[];
 
-  public removedScripts: readonly IScript[];
+  public removedScripts: readonly Script[];
 
-  public changedScripts: readonly IScript[];
+  public changedScripts: readonly Script[];
 
   public isEmpty(): boolean {
     throw new Error('Method not implemented.');