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/CategoryCollectionSpecificUtilitiesStub.ts

@@ -0,0 +1,22 @@
+import type { IScriptCompiler } from '@/application/Parser/Executable/Script/Compiler/IScriptCompiler';
+import type { ILanguageSyntax } from '@/application/Parser/Executable/Script/Validation/Syntax/ILanguageSyntax';
+import type { CategoryCollectionSpecificUtilities } from '@/application/Parser/Executable/CategoryCollectionSpecificUtilities';
+import { ScriptCompilerStub } from './ScriptCompilerStub';
+import { LanguageSyntaxStub } from './LanguageSyntaxStub';
+
+export class CategoryCollectionSpecificUtilitiesStub
+implements CategoryCollectionSpecificUtilities {
+  public compiler: IScriptCompiler = new ScriptCompilerStub();
+
+  public syntax: ILanguageSyntax = new LanguageSyntaxStub();
+
+  public withCompiler(compiler: IScriptCompiler) {
+    this.compiler = compiler;
+    return this;
+  }
+
+  public withSyntax(syntax: ILanguageSyntax) {
+    this.syntax = syntax;
+    return this;
+  }
+}