Tests

chore: clean linter warnings + remove mypy continue-on-error (closes … #42

Job	Run time
Typecheck (mypy)	20s
Secret scan (gitleaks)	5s
Unit tests (ubuntu-latest / Python 3.13)	15s
Unit tests (ubuntu-latest / Python 3.12)	15s
Unit tests (ubuntu-latest / Python 3.11)	10s
	1m 5s

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