fix: fallback to default width when terminal size is 0 (#17946)

[thiago-carbonera]

Resolves #17946

Problem Description

The bug occurred specifically when running help commands (pants help) within the Emacs editor's eshell terminal. Because it is a more limited environment, eshell incorrectly reported the terminal width as 0 columns.
The function responsible for calculating this width (terminal_width), located in the docutil.py file, used the shutil.get_terminal_size() method to capture the value. Upon receiving the value 0, the function simply subtracted a standard padding of 2. This mathematical calculation resulted in a negative width of -2. Consequently, when the system attempted to format the help text to fit on an impossible -2 column screen, the program suffered a total collapse, triggering the fatal error ValueError: invalid width -2 (must be > 0).

What changed:

Refactored terminal_width in docutil.py to explicitly check if shutil.get_terminal_size().columns returns 0.

If columns == 0 (which happens in limited terminals like Emacs eshell), the function now applies the default fallback value before subtracting the padding, preventing a ValueError with negative widths.

Added a regression test (test_terminal_width_falls_back_when_columns_are_zero) in docutil_test.py to ensure the fallback logic holds via monkeypatching.

[benjyw]

Thanks for the fix! If you could add that comment, then I'll run CI.

[benjyw]

A naive reader might see this as redundant due to the prior use of thefallback argument to get_terminal_size(). So a comment explaining that some limited terminals may report a width of 0 would be great.

[benjyw]

The CI failures are real: The test and lint errors need fixing, and please add an entry in the release notes at docs/notes/2.33.x.md