test: skip jax-backed tests when jax is absent (Python matrix)

These tests exercise jax-only code paths (vmapped profiles / blackjax NUTS /
nufft sparse operator / use_jax=True), so they need jax installed to run — it
ships via the [optional] extras and is present in the per-repo CI (3.12/3.13).
The PyAutoBuild Python Version Matrix installs the NumPy-only stack (and jax
can't install on 3.9 anyway), so guard the 1 affected test(s) with a
skipif on jax availability rather than letting them ModuleNotFoundError.
Numpy-only tests in the same files are unaffected.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: 2 people

test_autoarray/inversion/pixelization/interpolator/test_knn_barycentric.py

@@ -1,10 +1,20 @@
+import importlib.util
+
 import numpy as np
 import pytest
 
 from autoarray.inversion.mesh.interpolator.knn import (
     barycentric_weights_from_3_nearest,
 )
 
+# The kNN weight computation is jax-backed; these tests need jax installed to
+# run (it ships via the `[optional]` extras). The NumPy-only Python-version
+# matrix has no jax, so skip there rather than fail.
+requires_jax = pytest.mark.skipif(
+    importlib.util.find_spec("jax") is None,
+    reason="requires jax (installed via the [optional] extras; absent on the NumPy-only matrix env)",
+)
+
 
 def test__weights__interior_query_matches_delaunay_exactly():
     mesh = np.array([[0.0, 0.0], [1.0, 0.0], [0.0, 1.0]])
@@ -129,6 +139,7 @@ def test__mesh_class__inherits_knn_knobs():
     assert mesh.split_neighbor_division == 2
 
 
+@requires_jax
 def test__interpolator__numpy_path_returns_writable_mappings_and_weights():
     """
     Regression guard: on the numpy path, `mappings` and `weights` must be