ci: fix coverage

[flying-sheep]

One more thing was necessary to have this work like hatch test -pc: COVERAGE_PROCESS_START needs to be set!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.69%. Comparing base (57c3f3e) to head (66a8307).
⚠️ Report is 57 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2115       +/-   ##
===========================================
+ Coverage   31.84%   85.69%   +53.85%     
===========================================
  Files          46       46               
  Lines        7090     7090               
===========================================
+ Hits         2258     6076     +3818     
+ Misses       4832     1014     -3818     

see 34 files with indirect coverage changes

[flying-sheep]

just requesting your review so you can see. it works!