Function ensureDirectoryExists

ensureDirectoryExists(dirName: string): void
Ensures a directory exists, creating it if necessary. Creates parent directories recursively.
Parameters
- dirName: string
  Directory name/path relative to current working directory
Returns void
Example
```
ensureDirectoryExists('testsets');
ensureDirectoryExists('nested/path/to/dir');
```
- Defined in helpers/utils.ts:259