run pre-commit on all files, convert to ruff

[sritchie]

This PR:

• runs the pre-commit hooks on all files
• converts to the Ruff formatter + the pre-commit config currently used by genlm-{backend, grammar, control}

[gabegrand]

LGTM, thanks!

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 20 lines in your changes missing coverage. Please review.

Project coverage is 66.00%. Comparing base (3aacd9b) to head (c46679e).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
hfppl/llms.py	50.00%	18 Missing ⚠️
hfppl/chunks.py	50.00%	1 Missing ⚠️
hfppl/distributions/lmcontext.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #29      +/-   ##
==========================================
- Coverage   66.05%   66.00%   -0.05%     
==========================================
  Files          17       17              
  Lines         710      709       -1     
==========================================
- Hits          469      468       -1     
  Misses        241      241              

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