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/checks/desktop-runtime-errors/check-desktop-runtime-errors/app/app-logs.ts

@@ -63,9 +63,24 @@ async function determineLogPath(
   const logFilePaths: {
     readonly [K in SupportedPlatform]: () => string;
   } = {
-    [SupportedPlatform.macOS]: () => join(process.env.HOME, 'Library', 'Logs', appName, `${logFileName}.log`),
-    [SupportedPlatform.Linux]: () => join(process.env.HOME, '.config', appName, 'logs', `${logFileName}.log`),
-    [SupportedPlatform.Windows]: () => join(process.env.USERPROFILE, 'AppData', 'Roaming', appName, 'logs', `${logFileName}.log`),
+    [SupportedPlatform.macOS]: () => {
+      if (!process.env.HOME) {
+        throw new Error('HOME environment variable is not defined');
+      }
+      return join(process.env.HOME, 'Library', 'Logs', appName, `${logFileName}.log`);
+    },
+    [SupportedPlatform.Linux]: () => {
+      if (!process.env.HOME) {
+        throw new Error('HOME environment variable is not defined');
+      }
+      return join(process.env.HOME, '.config', appName, 'logs', `${logFileName}.log`);
+    },
+    [SupportedPlatform.Windows]: () => {
+      if (!process.env.USERPROFILE) {
+        throw new Error('USERPROFILE environment variable is not defined');
+      }
+      return join(process.env.USERPROFILE, 'AppData', 'Roaming', appName, 'logs', `${logFileName}.log`);
+    },
   };
   const logFilePath = logFilePaths[CURRENT_PLATFORM]?.();
   if (!logFilePath) {