test(conftest): remove jax from conftest entirely (numpy-only rule)

Per the 'library unit tests stay numpy-only' rule, conftest must not
import jax at all — not even via try/except. Replace the eager
import + jax.config.update + jnp.sum-warmup with a find_spec-gated
collect_ignore_glob that skips test_jax_*.py files when jax isn't
installed. find_spec checks availability without importing.

This supersedes the prior try/except approach in 07fcc0e.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

Author: 2 people

test_autoarray/conftest.py

@@ -1,18 +1,4 @@
-try:
-    import jax
-    import jax.numpy as jnp
-
-    jax.config.update("jax_enable_x64", True)
-    _JAX_AVAILABLE = True
-except ImportError:
-    _JAX_AVAILABLE = False
-
-
-def pytest_configure():
-    if _JAX_AVAILABLE:
-        _ = jnp.sum(jnp.array([0.0]))  # Force backend init
-
-
+import importlib.util
 import os
 from os import path
 import pytest
@@ -21,6 +7,13 @@ def pytest_configure():
 from autoarray import fixtures
 from autoconf import conf
 
+# Skip JAX-only tests when jax isn't installed. find_spec checks availability
+# WITHOUT importing the module, so this conftest stays numpy-only per the
+# "library unit tests stay numpy-only" rule.
+collect_ignore_glob = []
+if importlib.util.find_spec("jax") is None:
+    collect_ignore_glob = ["test_jax_*.py", "**/test_jax_*.py"]
+
 
 class PlotPatch:
     def __init__(self):