[Fix] Register triton.runtime.cache.triton_key in the MPS stub so torch.compile keeps working (#37937)

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

test/registered/unit/platforms/test_mps_triton_stub.py

@@ -40,6 +40,25 @@ assert _KernelType is not None
             msg=f"stdout={completed.stdout}\nstderr={completed.stderr}",
         )
 
+    def test_torch_compile_works_after_sglang_installs_stub(self):
+        script = """
+import sglang
+import torch
+torch.compile(lambda x: x * 2 + 1)(torch.randn(8))
+"""
+        completed = subprocess.run(
+            [sys.executable, "-c", script],
+            capture_output=True,
+            text=True,
+            timeout=60,
+            check=False,
+        )
+        self.assertEqual(
+            completed.returncode,
+            0,
+            msg=f"stdout={completed.stdout}\nstderr={completed.stderr}",
+        )
+
 
 if __name__ == "__main__":
     unittest.main()