Should handle "besides for"

I just heard this for the first time in a ThePrimeagen video:
> There were a few cases where it's actually pretty sweet, but **besides for** that, it was largely ineffective.

This is a known mistake that's covered [by ludwig.guru](https://ludwig.guru/s/Besides+for) and [by Stack Exchange](https://ell.stackexchange.com/questions/48316).

And it's not rare on GitHub:
- **Besides for** multilevel verbosity you usually do -vv or -vvv, which won't work for Nettacker because we don't have any "extra" logs
- **Besides for** providing practical tools, KTH_Toolbox also defines a convenient framework for developing new ones.
- Without it, the feature is, **besides for** basic testing with small corpuses of text, not useable.
- No autocomplete **besides for** classes that are in the same file I'm editing.

Ludwig recommends replacing with just "besides" but I'd say "other than" is at least as good, if not better.

There may be false positives where people have instead just omitted a comma between "besides" and "for", which is a totally different construction.

No file or test is named in the issue. Start by locating how Harper represents and tests grammar patterns, then use the reported “besides for” examples to understand the intended match. Done means detecting the mistaken construction while preserving valid comma-separated uses of “besides” and “for”.

Written by the indexing model from the issue text.