fix: track batch position delete references

[u70b3]

Summary

• collect referenced data-file paths when writing position deletes as an Arrow batch
• update referenced-path metadata only after the underlying write succeeds
• reject null batch inputs, null file paths, and sliced (non-zero offset) batches
• cover single-file, multi-file, mixed, empty, invalid, and failed-then-successful batches

Testing

• pre-commit run --files src/iceberg/data/position_delete_writer.cc src/iceberg/test/data_writer_test.cc
• build-gcc14/src/iceberg/test/data_test (159 tests passed)
• git diff --check

[u70b3]

Hi @wgtmac, gentle ping for a review when you have a moment. This has been sitting for about two weeks; all CI checks are green and it merges cleanly against the latest main. The change tracks referenced data-file paths for batch position-delete writes so referenced_data_file and bounds metadata match the WriteDelete path, and hardens ownership/validation for rejected batches. Thanks!