fix: fix tests and some typing

[tlambert03]

fixes #21

[codecov]

Codecov Report

Attention: Patch coverage is 90.00000% with 5 lines in your changes missing coverage. Please review.

Project coverage is 79.51%. Comparing base (0619a02) to head (f7d3b91).

Files with missing lines	Patch %	Lines
src/scenex/model/_canvas.py	0.00%	3 Missing ⚠️
src/scenex/adaptors/_registry.py	0.00%	1 Missing ⚠️
src/scenex/model/_view.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #22      +/-   ##
==========================================
+ Coverage   77.66%   79.51%   +1.84%     
==========================================
  Files          42       42              
  Lines        1500     1523      +23     
==========================================
+ Hits         1165     1211      +46     
+ Misses        335      312      -23     

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