[ROCm] Skip core_test reduction autotuner failures on Navi/RDNA GPUs (gfx11xx)

[CSkmd]

Description

Short-term CI unblock for ROCM-21429.

Adds skip markers to three failing core_test.py tests on ROCm Navi/RDNA
devices, following the pattern established in #720. The skip uses
"Radeon" in device_kind to detect RDNA hardware.

This is a short-term fix to unblock CI. The proper fix requires changes to
openxla/xla — see the analysis comment and ROCM-21429 for details.

Follows skip pattern from #720.

Changes

Affected tests:

• CoreTest::test_simple_jit
• CoreTest::test_tracer_reprs
• CoreTest::test_verbose_tracer_reprs

   def test_simple_jit(self):
+    if (jtu.is_device_rocm()
+        and "Radeon" in jax.local_devices()[0].device_kind):
+      self.skipTest(
+          "XLA reduction autotuner has no valid config for Navi/RDNA GPUs (gfx11xx)")
     def foo(x):

   def test_tracer_reprs(self):
+    if (jtu.is_device_rocm()
+        and "Radeon" in jax.local_devices()[0].device_kind):
+      self.skipTest(
+          "XLA reduction autotuner has no valid config for Navi/RDNA GPUs (gfx11xx)")
     def f(x):

   def test_verbose_tracer_reprs(self):
+    if (jtu.is_device_rocm()
+        and "Radeon" in jax.local_devices()[0].device_kind):
+      self.skipTest(
+          "XLA reduction autotuner has no valid config for Navi/RDNA GPUs (gfx11xx)")
     # Verbose reprs, avaiable via tracer._pretty_print()

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This PR was generated with AI assistance (Claude Code).