fix: improve stacklevel in register() warning for better traceback

The register() method's warning about non-ImageReader instances now uses
stacklevel=3 instead of stacklevel=2. This correctly points to the LoadImage()
call site where the reader is being instantiated, rather than internal frames.

Stack trace:
- User code: LoadImage(reader=...)
- LoadImage.__init__()
- self.register()
- warnings.warn(stacklevel=3) → points to LoadImage() call

This improves debugging experience for users who pass invalid readers.

Signed-off-by: Cipher <cipher@openclaw.ai>

Author: Cipher

monai/transforms/io/array.py

@@ -248,7 +248,7 @@ def register(self, reader: ImageReader):
         """
         if not isinstance(reader, ImageReader):
             warn_msg = f"Preferably the reader should inherit ImageReader, but got {type(reader)}."
-            warnings.warn(warn_msg, stacklevel=2)
+            warnings.warn(warn_msg, stacklevel=3)
         self.readers.append(reader)
 
     def __call__(self, filename: Sequence[PathLike] | PathLike, reader: ImageReader | None = None):