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/TheSearchBar.vue

@@ -38,11 +38,12 @@ export default defineComponent({
       const { totalScripts } = currentState.value.collection;
       return `Search in ${totalScripts} scripts`;
     });
-    const searchQuery = ref<string>();
+
+    const searchQuery = ref<string | undefined>();
 
     watch(searchQuery, (newFilter) => updateFilter(newFilter));
 
-    function updateFilter(newFilter: string) {
+    function updateFilter(newFilter: string | undefined) {
       modifyCurrentState((state) => {
         const { filter } = state;
         if (!newFilter) {
@@ -61,7 +62,7 @@ export default defineComponent({
     }, { immediate: true });
 
     function updateFromInitialFilter(filter?: IFilterResult) {
-      searchQuery.value = filter?.query || '';
+      searchQuery.value = filter?.query;
     }
 
     function subscribeToFilterChanges(