[MPS] Fix Triton stub sub-module imports on Python 3.12+ (#21551)

Co-authored-by: karanb192 <karan@example.com>
Co-authored-by: R0CKSTAR <yeahdongcn@gmail.com>
Co-authored-by: R0CKSTAR <xiaodong.ye@mthreads.com>

python/sglang/_triton_stub.py

@@ -125,24 +125,22 @@ class _TritonFinder:
     ``triton.*`` sub-module that isn't already in ``sys.modules``.
     """
 
-    def find_module(self, fullname, path=None):
+    def find_spec(self, fullname, path=None, target=None):
+        """PEP 451 meta-path finder for ``triton.*`` sub-modules."""
         if fullname == "triton" or fullname.startswith("triton."):
-            return self
-        return None
-
-    def load_module(self, fullname):
             if fullname in sys.modules:
-            return sys.modules[fullname]
+                return getattr(sys.modules[fullname], "__spec__", None)
+            # Create and register the mock so the import machinery finds it
             mod = _MockModule(fullname)
             sys.modules[fullname] = mod
-        # Wire up the parent relationship
             parts = fullname.rsplit(".", 1)
             if len(parts) == 2:
                 parent_name, child_name = parts
                 parent = sys.modules.get(parent_name)
                 if parent is not None:
                     setattr(parent, child_name, mod)
-        return mod
+            return mod.__spec__
+        return None
 
 
 def _make_mock(name: str) -> _MockModule: