Refactor text utilities and expand their usage

This commit refactors existing text utility functions into the
application layer for broad reuse and integrates them across
the codebase. Initially, these utilities were confined to test
code, which limited their application.

Changes:

- Move text utilities to the application layer.
- Centralize text utilities into dedicated files for better
  maintainability.
- Improve robustness of utility functions with added type checks.
- Replace duplicated logic with centralized utility functions
  throughout the codebase.
- Expand unit tests to cover refactored code parts.

tests/unit/application/Context/State/Code/Event/CodeChangedEvent.spec.ts

@@ -5,6 +5,7 @@ import { CodePosition } from '@/application/Context/State/Code/Position/CodePosi
 import { SelectedScriptStub } from '@tests/unit/shared/Stubs/SelectedScriptStub';
 import { ScriptStub } from '@tests/unit/shared/Stubs/ScriptStub';
 import type { SelectedScript } from '@/application/Context/State/Selection/Script/SelectedScript';
+import { collectExceptionMessage } from '@tests/unit/shared/ExceptionCollector';
 
 describe('CodeChangedEvent', () => {
   describe('ctor', () => {
@@ -19,16 +20,34 @@ describe('CodeChangedEvent', () => {
           [new SelectedScriptStub(new ScriptStub('2')), new CodePosition(0, nonExistingLine2)],
         ]);
         // act
-        let errorText = '';
-        try {
+        const actualErrorMessage = collectExceptionMessage(() => {
           new CodeChangedEventBuilder()
             .withCode(code)
             .withNewScripts(newScripts)
             .build();
-        } catch (error) { errorText = error.message; }
+        });
         // assert
-        expect(errorText).to.include(nonExistingLine1);
-        expect(errorText).to.include(nonExistingLine2);
+        expect(actualErrorMessage).to.include(nonExistingLine1);
+        expect(actualErrorMessage).to.include(nonExistingLine2);
+      });
+      it('invalid line position validation counts empty lines', () => {
+        // arrange
+        const totalEmptyLines = 5;
+        const code = '\n'.repeat(totalEmptyLines);
+        // If empty lines would not be counted, this would result in error
+        const existingLineEnd = totalEmptyLines;
+        const newScripts = new Map<SelectedScript, ICodePosition>([
+          [new SelectedScriptStub(new ScriptStub('1')), new CodePosition(0, existingLineEnd)],
+        ]);
+        // act
+        const act = () => {
+          new CodeChangedEventBuilder()
+            .withCode(code)
+            .withNewScripts(newScripts)
+            .build();
+        };
+        // assert
+        expect(act).to.not.throw();
       });
       describe('does not throw with valid code position', () => {
         // arrange