Place cython-test .so in tests/cython regardless of cwd

tests/cython/build_tests.py runs `build_ext --inplace`, which writes the
compiled .so relative to the current working directory. pixi runs the
build-cython-tests task from the project root, so the .so landed in the
package root instead of tests/cython/, where pytest imports it by bare module
name. The test only passed previously because a correctly-placed .so from an
earlier build persisted (gitignored); a clean checkout fails with
ModuleNotFoundError.

chdir to the script directory before build_ext --inplace so the .so lands next
to its .pyx in both cuda_bindings and cuda_core (kept aligned per #1978).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: rparolin

cuda_bindings/tests/cython/build_tests.py

@@ -12,6 +12,7 @@
 
 from __future__ import annotations
 
+import os
 import sys
 from pathlib import Path
 
@@ -45,6 +46,13 @@ def main() -> None:
         compiler_directives={"freethreading_compatible": True},
     )
 
+    # `build_ext --inplace` places the compiled .so relative to the current
+    # working directory, but pixi runs this task from the project root. pytest
+    # imports each extension by bare module name (see test_cython.py), which
+    # only resolves when the .so sits in tests/cython (the dir pytest puts on
+    # sys.path). chdir here so the .so lands next to its .pyx regardless of the
+    # invoking cwd.
+    os.chdir(script_dir)
     sys.argv = [sys.argv[0], "build_ext", "--inplace"]
     setup(name="cuda_bindings_cython_tests", ext_modules=ext_modules)
 

cuda_core/tests/cython/build_tests.py

@@ -12,6 +12,7 @@
 
 from __future__ import annotations
 
+import os
 import sys
 from pathlib import Path
 
@@ -44,6 +45,13 @@ def main() -> None:
         compiler_directives={"freethreading_compatible": True},
     )
 
+    # `build_ext --inplace` places the compiled .so relative to the current
+    # working directory, but pixi runs this task from the project root. pytest
+    # imports each extension by bare module name (see test_cython.py), which
+    # only resolves when the .so sits in tests/cython (the dir pytest puts on
+    # sys.path). chdir here so the .so lands next to its .pyx regardless of the
+    # invoking cwd.
+    os.chdir(script_dir)
     sys.argv = [sys.argv[0], "build_ext", "--inplace"]
     setup(name="cuda_core_cython_tests", ext_modules=ext_modules)