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/application/Parser/Executable/Script/Validation/Rules/NoEmptyLines.spec.ts

@@ -0,0 +1,46 @@
+import { describe } from 'vitest';
+import { NoEmptyLines } from '@/application/Parser/Executable/Script/Validation/Rules/NoEmptyLines';
+import { testCodeValidationRule } from './CodeValidationRuleTestRunner';
+
+describe('NoEmptyLines', () => {
+  describe('analyze', () => {
+    testCodeValidationRule([
+      {
+        testName: 'no results when code is valid',
+        codeLines: ['non-empty-line1', 'none-empty-line2'],
+        expected: [],
+        sut: new NoEmptyLines(),
+      },
+      {
+        testName: 'shows error for empty line',
+        codeLines: ['first line', '', 'third line'],
+        expected: [{ index: 2, error: 'Empty line' }],
+        sut: new NoEmptyLines(),
+      },
+      {
+        testName: 'shows error for multiple empty lines',
+        codeLines: ['first line', '', 'third line', ''],
+        expected: [2, 4].map((index) => ({ index, error: 'Empty line' })),
+        sut: new NoEmptyLines(),
+      },
+      {
+        testName: 'shows error for whitespace-only lines',
+        codeLines: ['first line', '  ', 'third line'],
+        expected: [{ index: 2, error: 'Empty line: "{whitespace}{whitespace}"' }],
+        sut: new NoEmptyLines(),
+      },
+      {
+        testName: 'shows error for tab-only lines',
+        codeLines: ['first line', '\t\t', 'third line'],
+        expected: [{ index: 2, error: 'Empty line: "{tab}{tab}"' }],
+        sut: new NoEmptyLines(),
+      },
+      {
+        testName: 'shows error for lines that consists of whitespace and tabs',
+        codeLines: ['first line', '\t \t', 'third line', ' \t '],
+        expected: [{ index: 2, error: 'Empty line: "{tab}{whitespace}{tab}"' }, { index: 4, error: 'Empty line: "{whitespace}{tab}{whitespace}"' }],
+        sut: new NoEmptyLines(),
+      },
+    ]);
+  });
+});