fix: request signature with annotation format STRING

[mschoettle]

On Python 3.14+ the default annotation format is Format.VALUE which causes an error when requesting a signature with an undefined name.

On Python 3.14, ruff suggests to move certain imports into type checking blocks, leading for example to the following:

from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from _pytest.config import Config
    from _pytest.main import Session
    from _pytest.python import Function

def pytest_collection_modifyitems(session: Session, config: Config, items: list[Function]) -> None:
    ...

Causing:

.venv/lib/python3.14/site-packages/pluggy/_manager.py:161: in register
    hookimpl = HookImpl(plugin, plugin_name, method, hookimpl_opts)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.venv/lib/python3.14/site-packages/pluggy/_hooks.py:664: in __init__
    argnames, kwargnames = varnames(self.function)
                           ^^^^^^^^^^^^^^^^^^^^^^^
.venv/lib/python3.14/site-packages/pluggy/_hooks.py:313: in varnames
    sig = inspect.signature(
../../../../../.local/share/uv/python/cpython-3.14.4-macos-aarch64-none/lib/python3.14/inspect.py:3323: in signature
    return Signature.from_callable(obj, follow_wrapped=follow_wrapped,
../../../../../.local/share/uv/python/cpython-3.14.4-macos-aarch64-none/lib/python3.14/inspect.py:3038: in from_callable
    return _signature_from_callable(obj, sigcls=cls,
../../../../../.local/share/uv/python/cpython-3.14.4-macos-aarch64-none/lib/python3.14/inspect.py:2512: in _signature_from_callable
    return _signature_from_function(sigcls, obj,
../../../../../.local/share/uv/python/cpython-3.14.4-macos-aarch64-none/lib/python3.14/inspect.py:2335: in _signature_from_function
    annotations = get_annotations(func, globals=globals, locals=locals, eval_str=eval_str,
../../../../../.local/share/uv/python/cpython-3.14.4-macos-aarch64-none/lib/python3.14/annotationlib.py:966: in get_annotations
    ann = _get_dunder_annotations(obj)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
../../../../../.local/share/uv/python/cpython-3.14.4-macos-aarch64-none/lib/python3.14/annotationlib.py:1159: in _get_dunder_annotations
    ann = getattr(obj, "__annotations__", None)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
opal/conftest.py:45: in __annotate__
    def pytest_collection_modifyitems(session: Session, config: Config, items: list[Function]) -> None:
                                               ^^^^^^^
E   NameError: name 'Session' is not defined

Changing the annotation format to STRING fixes this.

[mschoettle]

This is reported as uncovered despite the comment

[mschoettle]

Actually, with the combined coverage data the comment should not be required. Not sure what's wrong with the codecov check.

[mschoettle]

Should be fixed once #669 is merged

[RonnyPfannschmidt]

note - this may be super-seeded by #632 which i just picked up again

[mschoettle]

Yes indeed. inspect.signature is not called anymore with that change.