docs: missing docstrings in `ensure_sorted.py`

[maptoan]

Description

The Category class and its methods (add_app, is_sorted, where_unsorted, how_to_sort), as well as the main function, lack docstrings. This makes it harder for future maintainers to understand the purpose, arguments, and return values of these components without reading the entire implementation. Given this script is part of the CI pipeline, its clarity is important for project health and maintainability.

Severity: medium
File: ensure_sorted.py

Expected Behavior

The code should handle this case properly to avoid unexpected errors or degraded quality.

[offa]

See my comment in #622.

[offa]

Since issue #622 has already been closed, I assume this issue is resolved.