[Python] DataFrame interchange silently corrupts non-native-endian columns.

[tam3tamtam]

Describe the bug, including details regarding any error messages, version, and platform.

Describe the bug, including details regarding any error messages, version, and platform.

pyarrow.interchange.from_dataframe can return incorrect values for columns
whose interchange-protocol dtype uses non-native endianness. The importer
interprets the producer's data buffer as native-endian without accounting for
the endianness field. No error is raised; the values are silently corrupted.

This was reproduced with PyArrow 26.0.0 (development build) on macOS arm64
with Python 3.13.15. The same issue can affect non-native-endian string offset
buffers.

Reproduction

import numpy as np
import pandas as pd
import pyarrow.interchange as pai

df = pd.DataFrame({"value": np.array([1, 2, 300], dtype=">i4")})
table = pai.from_dataframe(df)
print(table["value"].to_pylist())

Actual behavior

On a little-endian platform, this prints values interpreted with the wrong byte
order, for example:

[16777216, 33554432, 738263040]

Expected behavior

The imported values should preserve the producer's values:

[1, 2, 300]

Proposed fix

Convert non-native-endian data and string offset buffers to native byte order
when copying is allowed. If conversion requires a copy and allow_copy=False,
raise a RuntimeError.

Component(s)

Python

[tam3tamtam]

I would like to work on this issue.