Fix import and formatting issues in multiple files

[tlambert03]

This pull request fixes import and formatting issues in multiple files. The changes include:

• Removed unused import in tests/test_matslines.py

• Added missing import in src/microsim/__init__.py

• Fixed formatting in src/microsim/_operator.py

• Removed unused code in src/microsim/models/_sample.py

• Fixed formatting in src/microsim/samples/_bresenham.py

• Fixed formatting in src/microsim/samples/_matslines.py

• Removed unused code in src/microsim/models/_camera.py

• Fixed formatting in src/microsim/models/_renderable.py

• Fixed formatting in src/microsim/util.py

• Fixed formatting in src/microsim/illum/_sim.py

• Fixed formatting in src/microsim/samples/_cosem.py

• Updated pre-commit hooks in .pre-commit-config.yaml

• Added thoughts.md file

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