fix: Support text partitioning from ZipExtFile objects

[dsolankii]

Fixes #4097.

Summary

This PR fixes partitioning for text files opened from ZIP archives using Python's zipfile module.

zipfile.ZipFile.open() returns a ZipExtFile object. ZipExtFile is a readable file-like object, but convert_to_bytes() previously only accepted a limited set of concrete file-like types. As a result, text files inside ZIP archives failed during encoding detection with an Invalid file-like object type error.

This change updates convert_to_bytes() to support generic readable file-like objects while preserving the original stream position when possible.

Changes

• Added support for generic readable file-like objects in convert_to_bytes().
• Preserved stream position for seekable file-like objects.
• Added regression coverage for partitioning a text file from a ZipExtFile object.
• Added unit coverage to verify that convert_to_bytes() preserves the position of seekable streams.

How to test

Run the targeted tests:

python -m pytest \
  test_unstructured/partition/test_auto.py::test_partition_txt_from_zip_ext_file \
  test_unstructured/partition/common/test_common.py::test_convert_to_bytes_preserves_seekable_file_position \
  -q

Expected result:

2 passed

Validation

I reproduced the issue locally before applying the fix. Partitioning a text file from a ZIP archive failed with:

ValueError: Invalid file-like object type

After the fix, the same flow successfully returns partitioned text elements.

[dsolankii]

@cragwolfe Would you please review?

[dsolankii]

@badGarnet Would you please review this PR , its been 2 week.