Fix file retention after updates on macOS #417

This fixes issue #417 where autoupdate installer files were not deleted
on macOS, leading to accumulation of old installers.

Key changes:

- Store update files in application-specific directory
- Clear update files directory on every app launch

Other supporting changes:

- Refactor file system operations to be more testable and reusable
- Improve separation of concerns in directory management
- Enhance dependency injection for auto-update logic
- Fix async completion to support `await` operations
- Add additional logging and revise some log messages during updates

tests/unit/shared/ExceptionCollector.ts

@@ -12,7 +12,19 @@ function collectException(
     error = err;
   }
   if (!error) {
-    throw new Error('action did not throw');
+    throw new Error('Action did not throw');
+  }
+  return error;
+}
+
+export async function collectExceptionAsync(
+  action: () => Promise<unknown>,
+): Promise<Error | undefined> {
+  let error: Error | undefined;
+  try {
+    await action();
+  } catch (err) {
+    error = err;
   }
   return error;
 }