Make --watch-files work in dumb terminals and non-fancy input

[ekr1]

Currently, if cecli is run with TERM=dumb and/or --no-fancy-input, the option --watch-files does nothing, because it calls a blocking input method (and does not recognize any kind of interrupts).

This PR changes this behavior so --watch-files works with the dumbest variation, while keeping all other input variations (TUI, fancy) unchanged:

$ TERM=dumb cecli --no-tui --no-fancy-input --watch-files

(In short, --watch-files should now work completely irrespective of any other options.)

It is implemented for Unix/POSIX only, as I have no access to a Windows machine; but if the user tries --watch-files and for some reason the (old) blocking input logic is activated it should fall back gracefully with a helpful warning on Windows.

[dwash96]

Ope, very interesting. Can you run the pre-commit hooks and update the tests for this?

[ekr1]

Ope, very interesting. Can you run the pre-commit hooks and update the tests for this?

Thanks for taking care of this, @dwash96. I've been buried in work recently and didn't have a chance to look into this so far. ;)