Python type hints with ty

[cclauss]

https://docs.astral.sh/ty seems to find lots of problems with our Python type hints.

ty check \
    --ignore=call-non-callable \
    --ignore=deprecated \
    --ignore=invalid-argument-type \
    --ignore=invalid-assignment \
    --ignore=invalid-return-type \
    --ignore=invalid-type-arguments \
    --ignore=no-matching-overload \
    --ignore=not-iterable \
    --ignore=not-subscriptable \
    --ignore=possibly-missing-submodule \
    --ignore=unresolved-attribute \
    --ignore=unresolved-import