feat: full type safety, improved CI testing

[tlambert03]

replaces #4

[codecov]

Codecov Report

❌ Patch coverage is 80.60345% with 45 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.19%. Comparing base (e016752) to head (3f8c893).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/bffile/_biofile.py	79.16%	25 Missing ⚠️
src/bffile/_jimports.py	63.63%	16 Missing ⚠️
src/bffile/_core_metadata.py	94.00%	3 Missing ⚠️
src/bffile/_java_stuff.py	94.44%	1 Missing ⚠️

❌ Your patch status has failed because the patch coverage (80.60%) is below the target coverage (85.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #15      +/-   ##
==========================================
+ Coverage   77.08%   77.19%   +0.11%     
==========================================
  Files           4        6       +2     
  Lines         419      557     +138     
==========================================
+ Hits          323      430     +107     
- Misses         96      127      +31     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.