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/ExecutableValidatorStub.ts

@@ -0,0 +1,57 @@
+import type { ExecutableData } from '@/application/collections/';
+import type { ExecutableValidator, ExecutableValidatorFactory } from '@/application/Parser/Executable/Validation/ExecutableValidator';
+import { StubWithObservableMethodCalls } from './StubWithObservableMethodCalls';
+
+export const createExecutableValidatorFactoryStub
+: ExecutableValidatorFactory = () => new ExecutableValidatorStub();
+
+export class ExecutableValidatorStub
+  extends StubWithObservableMethodCalls<ExecutableValidator>
+  implements ExecutableValidator {
+  private assertThrowsOnFalseCondition = true;
+
+  public withAssertThrowsOnFalseCondition(enableAssertThrows: boolean): this {
+    this.assertThrowsOnFalseCondition = enableAssertThrows;
+    return this;
+  }
+
+  public assertValidName(nameValue: string): this {
+    this.registerMethodCall({
+      methodName: 'assertValidName',
+      args: [nameValue],
+    });
+    return this;
+  }
+
+  public assertDefined(data: ExecutableData): this {
+    this.registerMethodCall({
+      methodName: 'assertDefined',
+      args: [data],
+    });
+    return this;
+  }
+
+  public assert(
+    validationPredicate: () => boolean,
+    errorMessage: string,
+  ): this {
+    this.registerMethodCall({
+      methodName: 'assert',
+      args: [validationPredicate, errorMessage],
+    });
+    if (this.assertThrowsOnFalseCondition) {
+      if (!validationPredicate()) {
+        throw new Error(`[${ExecutableValidatorStub.name}] Assert validation failed: ${errorMessage}`);
+      }
+    }
+    return this;
+  }
+
+  public createContextualErrorMessage(errorMessage: string): string {
+    this.registerMethodCall({
+      methodName: 'createContextualErrorMessage',
+      args: [errorMessage],
+    });
+    return `${ExecutableValidatorStub.name}: ${errorMessage}`;
+  }
+}