Core: Fix bin packing when target file size is smaller than a row

[010Soham]

What does this change do?

When write.target-file-size-bytes is smaller than a single row, bin packing computed a 0 row chunk size and PyArrow raised a ValueError. This change clamps the chunk size to at least 1, so writes still succeed (one row per batch/file when needed).

Why is this needed?

Fixes a crash when users set a small target file size and attempt to write large records.

How was this tested?

• make lint
• uv run python -m pytest tests/io/test_pyarrow.py -k "bin_pack_arrow_table" -v
• make test (timed out at ~42%)

Closes #2795

[Fokko]

Good catch @010Soham, thanks for fixing this 👍