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/electron/preload/NodeOsMapper.spec.ts

@@ -7,10 +7,10 @@ describe('NodeOsMapper', () => {
     describe('determines desktop OS', () => {
       // arrange
       interface IDesktopTestCase {
-        nodePlatform: NodeJS.Platform;
-        expectedOs: OperatingSystem;
+        readonly nodePlatform: NodeJS.Platform;
+        readonly expectedOs: ReturnType<typeof convertPlatformToOs>;
       }
-      const testCases: readonly IDesktopTestCase[] = [ // https://nodejs.org/api/process.html#process_process_platform
+      const testScenarios: readonly IDesktopTestCase[] = [ // https://nodejs.org/api/process.html#process_process_platform
         {
           nodePlatform: 'aix',
           expectedOs: undefined,
@@ -40,15 +40,18 @@ describe('NodeOsMapper', () => {
           expectedOs: OperatingSystem.Windows,
         },
       ];
-      testCases.forEach(({ nodePlatform, expectedOs }) => {
+      testScenarios.forEach(({ nodePlatform, expectedOs }) => {
         it(nodePlatform, () => {
           // act
           const actualOs = convertPlatformToOs(nodePlatform);
           // assert
           expect(actualOs).to.equal(expectedOs, printMessage());
+          function printResult(os: ReturnType<typeof convertPlatformToOs>): string {
+            return os === undefined ? 'undefined' : OperatingSystem[os];
+          }
           function printMessage(): string {
-            return `Expected: "${OperatingSystem[expectedOs]}"\n`
-              + `Actual: "${OperatingSystem[actualOs]}"\n`
+            return `Expected: "${printResult(expectedOs)}"\n`
+              + `Actual: "${printResult(actualOs)}"\n`
               + `Platform: "${nodePlatform}"`;
           }
         });