Uploading a file from an in-memory stream is impossible: both code paths are broken #140

OswExpress.upload_file / OswExpressFile document IO as an accepted source, but no in-memory stream can actually be uploaded. Two independent bugs:

1. The IO branch is unreachable.
https://github.com/OpenSemanticLab/osw-python/blob/main/src/osw/express.py#L638

elif isinstance(source, IO):
    data["source_file_controller"] = InMemoryController(stream=source)

IO (from typing_extensions, imported at express.py:25) is not runtime-checkable as a protocol:

>>> import io, typing_extensions as te
>>> isinstance(io.BytesIO(b"x"), te.IO)
False

So a BytesIO falls through to the ValueError at express.py:641, whose message advertises IO as valid.

2. InMemoryController cannot be constructed anyway.
https://github.com/OpenSemanticLab/osw-python/blob/main/src/osw/controller/file/memory.py#L21-L23

def __init__(self, **kwargs):
    self.stream = StringIO()
    super().__init__(**kwargs)

The assignment happens before the model is initialised:

>>> InMemoryController(stream=io.BytesIO(b"hi"))
AttributeError: 'osw.controller.file.memory.InMemoryController' object has no attribute '__iris__'

It also unconditionally overwrites a caller-supplied stream with an empty StringIO, and defaults to StringIO where the put/get counterparts are byte-oriented.

Suggested fix

• Replace the isinstance(source, IO) check with a duck-typed one (hasattr(source, "read")), or use typing.BinaryIO/io.IOBase.
• Drop the custom __init__ so pydantic assigns stream from kwargs, or set the default via a field default rather than in __init__.
• Add a test that round-trips a BytesIO through upload_file.

Context: found while planning the path-free MCP file tools (#133). That work routes around both by calling WikiFileController.put(file: IO) directly, so it is not blocked by this, but the public express API stays broken.