Fix latent run_checks crash and unblock mypy v2

[h-mayorquin]

The mypy bump to v2.1.0 on dev (13d0d67) surfaced a real latent bug in run_checks: when a caller passed progress_bar_class without also passing progress_bar_options, the default None was being splatted directly into the progress-bar constructor and would raise TypeError. This PR coalesces the kwargs to an empty dict before forwarding. The other change is a one-line annotation on available_checks in _registration.py to satisfy mypy 2.x's stricter var-annotated checking and has no behavior impact.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 82.81%. Comparing base (178dcd6) to head (5cc01e1).
⚠️ Report is 4 commits behind head on dev.

Files with missing lines	Patch %	Lines
src/nwbinspector/_nwb_inspection.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #701      +/-   ##
==========================================
+ Coverage   79.62%   82.81%   +3.18%     
==========================================
  Files          48       48              
  Lines        1890     1897       +7     
==========================================
+ Hits         1505     1571      +66     
+ Misses        385      326      -59     

Files with missing lines	Coverage Δ
src/nwbinspector/_registration.py	95.65% <100.00%> (ø)
src/nwbinspector/_nwb_inspection.py	85.90% <0.00%> (+4.02%)	⬆️

... and 4 files with indirect coverage changes

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