IO: Windows paths crash with 'Unrecognized filesystem type in URI: c' #3720

Apache Iceberg version

Latest main (also affects all released versions)

Please describe the bug

On Windows, passing a local absolute path (e.g. C:\Users\data\warehouse) to any PyIceberg IO operation crashes with:
from pyiceberg.io.pyarrow import PyArrowFileIO

io = PyArrowFileIO()
f = io.new_input(r"C:\Users\me\warehouse\table\metadata.json")
# ValueError: Unrecognized filesystem type in URI: c

an example from #1005 is:

from pyiceberg.catalog import load_catalog

catalog = load_catalog(
    "my_catalog",
    **{
        "type": "sql",
        "uri": "sqlite:///catalog.db",
        "warehouse": r"C:\Users\me\iceberg_warehouse",
    },
)
# UserWarning: No preferred file implementation for scheme: c

The root cause: Python's urlparse treats Windows drive letters as URI schemes (C:\... scheme='c'). Since 'c' is not in PyIceberg's scheme-to-FileIO mapping, all local file operations fail.

This affects three independent parse sites:

1. _infer_file_io_from_scheme() in pyiceberg/io/__init__.py
2. PyArrowFileIO.parse_location() in pyiceberg/io/pyarrow.py
3. FsspecFileIO._get_fs_from_uri() in pyiceberg/io/fsspec.py

Related issues

• infra: run tests for windows #2477 (CI: run tests on Windows lists this as the primary failure)
• Cannot specify "file://" uri or direct local file location for warehouse in Windows #1005 (user report closed as stale without fix)
• PR Enhance URI scheme validation for Windows paths #3161 (partial fix only pyarrow, no tests, went stale)
• PR Support execution in Windows using Local File System and NFS #996 (partial fix only pyarrow, went stale)

Proposed fix

A platform-guarded predicate that detects when urlparse has misidentified a Windows drive letter as a URI scheme, and remaps it to 'file':

import sys

def _is_windows_drive_letter(scheme: str) -> bool:
    return sys.platform == 'win32' and len(scheme) == 1 and scheme.isalpha()

Applied at all three parse sites. Zero behavior change on non-Windows (the platform check short-circuits). Includes platform-conditional tests.