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.

tests/unit/presentation/components/Scripts/View/Tree/TreeView/Node/Hierarchy/TreeNodeHierarchy.spec.ts

@@ -75,7 +75,7 @@ describe('TreeNodeHierarchy', () => {
 
   describe('depthInTree', () => {
     interface DepthTestScenario {
-      readonly parentNode: TreeNode,
+      readonly parentNode: TreeNode | undefined,
       readonly expectedDepth: number;
     }
     const testCases: readonly DepthTestScenario[] = [

tests/unit/presentation/components/Scripts/View/Tree/TreeView/Node/State/TreeNodeState.spec.ts

@@ -4,6 +4,7 @@ import { TreeNodeStateDescriptor } from '@/presentation/components/Scripts/View/
 import { TreeNodeCheckState } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/CheckState';
 import { NodeStateChangedEvent, TreeNodeStateTransaction } from '@/presentation/components/Scripts/View/Tree/TreeView/Node/State/StateAccess';
 import { PropertyKeys } from '@/TypeHelpers';
+import { expectExists } from '@tests/shared/Assertions/ExpectExists';
 
 describe('TreeNodeState', () => {
   describe('beginTransaction', () => {
@@ -37,14 +38,14 @@ describe('TreeNodeState', () => {
       const transaction = treeNodeState
         .beginTransaction()
         .withCheckState(TreeNodeCheckState.Checked);
-      let notifiedEvent: NodeStateChangedEvent;
+      let notifiedEvent: NodeStateChangedEvent | undefined;
       // act
       treeNodeState.changed.on((event) => {
         notifiedEvent = event;
       });
       treeNodeState.commitTransaction(transaction);
       // assert
-      expect(notifiedEvent).to.not.equal(undefined);
+      expectExists(notifiedEvent);
       expect(notifiedEvent.oldState.checkState).to.equal(TreeNodeCheckState.Unchecked);
       expect(notifiedEvent.newState.checkState).to.equal(TreeNodeCheckState.Checked);
     });

tests/unit/presentation/components/Scripts/View/Tree/TreeView/Node/TreeNodeManager.spec.ts

@@ -23,7 +23,7 @@ describe('TreeNodeManager', () => {
           const act = () => new TreeNodeManager(absentId);
           // assert
           expect(act).to.throw(expectedError);
-        });
+        }, { excludeNull: true, excludeUndefined: true });
       });
     });
 
@@ -37,14 +37,14 @@ describe('TreeNodeManager', () => {
         expect(node.metadata).to.equal(expectedMetadata);
       });
       describe('should accept absent metadata', () => {
-        itEachAbsentObjectValue((absentMetadata) => {
+        itEachAbsentObjectValue((absentValue) => {
           // arrange
-          const expectedMetadata = absentMetadata;
+          const expectedMetadata = absentValue;
           // act
           const node = new TreeNodeManager('id', expectedMetadata);
           // assert
-          expect(node.metadata).to.equal(absentMetadata);
-        });
+          expect(node.metadata).to.equal(undefined);
+        }, { excludeNull: true });
       });
     });
 

tests/unit/presentation/components/Scripts/View/Tree/TreeView/Node/UseKeyboardInteractionState.spec.ts

@@ -74,13 +74,16 @@ describe('useKeyboardInteractionState', () => {
 });
 
 function mountWrapperComponent(window: WindowWithEventListeners) {
-  let returnObject: ReturnType<typeof useKeyboardInteractionState>;
+  let returnObject: ReturnType<typeof useKeyboardInteractionState> | undefined;
   const wrapper = shallowMount(defineComponent({
     setup() {
       returnObject = useKeyboardInteractionState(window);
     },
     template: '<div></div>',
   }));
+  if (!returnObject) {
+    throw new Error('missing hook result');
+  }
   return {
     returnObject,
     wrapper,

tests/unit/presentation/components/Scripts/View/Tree/TreeView/Node/UseNodeState.spec.ts

@@ -57,7 +57,7 @@ describe('useNodeState', () => {
 });
 
 function mountWrapperComponent(nodeRef: Readonly<Ref<ReadOnlyTreeNode>>) {
-  let returnObject: ReturnType<typeof useNodeState>;
+  let returnObject: ReturnType<typeof useNodeState> | undefined;
   const wrapper = shallowMount(
     defineComponent({
       setup() {
@@ -74,6 +74,9 @@ function mountWrapperComponent(nodeRef: Readonly<Ref<ReadOnlyTreeNode>>) {
       },
     },
   );
+  if (!returnObject) {
+    throw new Error('missing hook result');
+  }
   return {
     wrapper,
     returnObject,