📝 **Task:** Implement `merge_themes(worker_outputs: list[list[str]]) -> list[tuple[str, int]]`: * Flatten all worker lists. * Normalise: `strip()` then `lower()`. Drop empty strings. * Count occurrences. * Return list sorted by count descending, ties broken alphabetically. Expected output for the demo workload: ``` [('shipping', 3), ('billing', 2), ('refund', 1)] ``` 📋 Implement the function above. Tests run automatically. 💡 **Hint:** Re-read the theory if stuck.