Fix CI failures from master merge: pyproject.toml syntax and deprecated test syntax

[Copilot]

Merge with master (#611) introduced two breaking issues preventing CI from running.

Changes

pyproject.toml - Fixed TOML syntax error in dev dependencies

 dev = [
     'ruff',
     'pytest',
     'pytest-cov',
     'sphinx',
-    'mypy'
+    'mypy',
     'pre-commit'
 ]

Merge conflict left missing comma between 'mypy' (from type hinting branch) and 'pre-commit' (from master), causing parser failure.

tests_core.py - Converted deprecated yield-based parameterization to @pytest.mark.parametrize

# Before (pytest <5.0 syntax, now removed)
def test_errors():
    classes = ['DataError']
    for subclass in classes:
        yield check_error, subclass

# After (modern pytest)
@pytest.mark.parametrize('subclass', ['DataError'])
def test_errors(subclass):
    import pySDC.core.errors
    err = getattr(pySDC.core.errors, subclass)
    try:
        raise err('bla')
    except err:
        assert True

Applied to test_errors, test_datatypes_mesh, and test_datatypes_particles. Removed now-unnecessary helper functions.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Type hinting</issue_title>
<issue_description>There are currently no type hints in core modules (or anywhere, for that matter). How hard would it be to add and test those comprehensively?</issue_description>

<agent_instructions>Run the CI test suite before finishing work to make sure everything works</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Type hinting #609

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