* Refactor: add pure pdf_ops module with real-PDF tests
* Drops tests we don't relly need + adds the typing annotation
* Now that I'm sure it works, re-work these tests to mock pdf_ops, rather than pikepdf
* Validates pages ahead of time in build_pdfs rather than during the building
* Adds the given/when/then and some additional cleanups of pytest style
* This is redundant now
* Chore: Refresh the mypy and pyrefly baselines
* Chore: Type factory calls as the model they build for mypy
factory-boy leaves Factory() unannotated, so mypy took UserFactory() to
be a factory instance rather than a User. A shared TypedModelFactory
base declares the call as returning the model for type checking only.
* Refresh again after rebase
Trenton H
