Refactor to enforce strictNullChecks

This commit applies `strictNullChecks` to the entire codebase to improve
maintainability and type safety. Key changes include:

- Remove some explicit null-checks where unnecessary.
- Add necessary null-checks.
- Refactor static factory functions for a more functional approach.
- Improve some test names and contexts for better debugging.
- Add unit tests for any additional logic introduced.
- Refactor `createPositionFromRegexFullMatch` to its own function as the
  logic is reused.
- Prefer `find` prefix on functions that may return `undefined` and
  `get` prefix for those that always return a value.

src/presentation/components/Scripts/Slider/HorizontalResizeSlider.vue

@@ -48,8 +48,12 @@ export default defineComponent({
     const firstElement = shallowRef<HTMLElement>();
 
     function onResize(displacementX: number): void {
-      const leftWidth = firstElement.value.offsetWidth + displacementX;
-      firstElement.value.style.width = `${leftWidth}px`;
+      const element = firstElement.value;
+      if (!element) {
+        throw new Error('The element reference ref is not correctly assigned to a DOM element.');
+      }
+      const leftWidth = element.offsetWidth + displacementX;
+      element.style.width = `${leftWidth}px`;
     }
 
     return {

src/presentation/components/Scripts/Slider/SliderHandle.vue

@@ -29,7 +29,10 @@ export default defineComponent({
     const cursorCssValue = 'ew-resize';
     let initialX: number | undefined;
 
-    const resize = (event) => {
+    const resize = (event: MouseEvent) => {
+      if (initialX === undefined) {
+        throw new Error('Resize action started without an initial X coordinate.');
+      }
       const displacementX = event.clientX - initialX;
       emit('resized', displacementX);
       initialX = event.clientX;