Commit the data files of the Iceberg test fixture

[robinskil]

Problem

Line 22 of .gitignore holds the pattern data/. This pattern also matches test-datasets/iceberg-example/data/.

Git tracks only the metadata/ folder of the fixture. The Parquet data files are absent.

The local suite raises FileNotFoundError. The S3 suite uploads a table without data files. The server answers:

Object at location iceberg-example/data/...parquet not found

Nine tests fail.

Failed tests

• test_iceberg.py (6 errors)
• test_iceberg_s3.py (3 failures)

Task

1. Add a negation rule for test-datasets/iceberg-example/data/ to .gitignore.
2. Regenerate the fixture:
   cargo test -p beacon-core --test iceberg_tables -- --ignored --exact regenerate_the_committed_fixture
3. Commit the data files.
4. Run both files again.

Environment

Branch features/reimplement-atlas. Image beacon-integration:local.