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.

src/application/Parser/Executable/Script/Validation/ICodeValidationRule.ts

@@ -0,0 +1,10 @@
+import type { ICodeLine } from './ICodeLine';
+
+export interface IInvalidCodeLine {
+  readonly index: number;
+  readonly error: string;
+}
+
+export interface ICodeValidationRule {
+  analyze(lines: readonly ICodeLine[]): IInvalidCodeLine[];
+}