Fix annoying pydantic warnings

[sneakers-the-rat]

Currently the test output is a total clusterfuck because of warnings emitted when writing the header data.

The warnings come because we're using model_construct() to create the header models, which skips the validation and coercion step, so we have numpy ints/floats instead of base python ints/floats. They serialize just fine, so it's safe to just ignore the warning there.

Also fixed a warning from python thinking we're trying to escape ``'['` instead of making a rich format string, so changed that to a raw string.

now there are no noisy warnings!

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📚 Documentation preview 📚: https://miniscope-io--74.org.readthedocs.build/en/74/

[sneakers-the-rat]

this one is uncontroversial so i'm just gonna YOLO merge it

[coveralls]

coverage: 77.17%. remained the same
when pulling a28f452 on fix-pydantic-serialization-warning
into 722552a on main.