fix(test): guard pyximport import for non-Cython tox envs

Author: keyz182

tests/unit/wiring/conftest.py

@@ -1,5 +1,12 @@
-"""Enable on-import compilation of the .pyx wiring fixture via pyximport."""
+"""Enable on-import compilation of the .pyx wiring fixture via pyximport.
 
-import pyximport
+Cython is not installed in every tox env (e.g. pydantic-{v1,v2}), so the
+import is guarded — test_cython.py skips at importorskip in that case.
+"""
 
-pyximport.install(language_level=3)
+try:
+    import pyximport
+
+    pyximport.install(language_level=3)
+except ImportError:
+    pass