chore: improve python-progressbar maintenance path

[lphuc2250gma]

Summary:

• Add narrow unit tests for edge cases in the utility helpers in progressbar/utils.py (e.g., len_color/no_color/AttributeBuffer behavior with empty strings, ANSI-only input, and mixed escape sequences) and tighten any missing type annotations on small helper functions. Purely additive tests plus minor type hint fixes — no behavior change.
• Keep the change narrow so it is straightforward to review.

Notes:

• I kept this scoped to the relevant implementation and tests.

[gemini-code-assist]

Code Review

This pull request updates the type hints for AttributeDict in progressbar/utils.py to support any value type and introduces a suite of unit tests for color-related utilities and dictionary behavior. The reviewer suggests explicitly importing the utils module in the test file to maintain consistency and recommends expanding the test coverage to include 24-bit TrueColor sequences and byte-based ANSI sequences for length calculations.

[gemini-code-assist]

The tests use progressbar.utils, but this submodule is not explicitly imported in the file. Given that progressbar.env is explicitly imported at line 6, it is recommended to also explicitly import progressbar.utils at the top of the file to ensure the tests run correctly and maintain consistency with the existing import style.

[gemini-code-assist]

Consider adding a test case for 24-bit (TrueColor) ANSI sequences to ensure they are also correctly stripped by no_color.

        ('\x1b[38;5;208mhello world\x1b[0m', 'hello world'),
        ('\x1b[38;2;255;0;0mred\x1b[0m', 'red'),

[gemini-code-assist]

While test_len_color includes an empty bytes case, it would be beneficial to add a test case for bytes containing ANSI escape sequences to ensure len_color handles bytes with formatting correctly, similar to the string cases.

Suggested change

	(b'', 0),
	(b'', 0),
	(b'\x1b[31mtext\x1b[0m', 4),