Add missing type annotations

[Danipulok]

What

• Annotate the parameters and returns that had none, so pyright no longer infers them as Unknown.
• Remove not_print in run_code.py, which nothing calls.
• Turn on four reportUnknown* rules so the gap cannot come back.
• Pin pythonVersion = "3.10" to match requires-python.

Why

Most of the package was annotated already, but a handful of parameters and returns were not, and nothing in the toolchain reported them.

typeCheckingMode = "strict" would be the blunt way to enforce it, but it is down to 6 diagnostics on this branch and none of them is a missing annotation: three are fixtures pyright cannot see being called or used across modules, two are request.node, which pytest leaves untyped deliberately, and one is the deprecated co_lnotab getter. The four rules cover exactly what this change is about and nothing else.

The pythonVersion pin matters on its own: without it pyright checks against whatever interpreter the job installed, 3.12 in CI today, so a 3.11-only annotation passes make typecheck and only surfaces in the 3.10 test job, if at all.

How to test

make lint, make typecheck, and make test-all-python for 3.10 through 3.14. No behaviour change, so the existing suite is unchanged.