Exact File-Version Compatibility Fixtures

These files were generated with the writers at baseline commit 3a72f8a61e14613f517dded6816d4bfc77817c93. The deterministic input batch is defined by compatibility_fixture_batch in src/compatibility_tests.rs and covers primitive, nullable UTF-8, nullable list, nullable dictionary, blob, multiple input batches, and multiple pages. The V2.0 embedded fixtures use the primitive and nullable UTF-8 columns from the first 257 rows of the same batch.

datagen.py copies the baseline-compatible datagen.rs into a clean checkout of that commit, runs it twice in separate processes with an isolated Cargo target directory, and verifies that both runs produce identical bytes:

git worktree add --detach /tmp/lance-exact-version-baseline \
    3a72f8a61e14613f517dded6816d4bfc77817c93
python3 rust/lance-file/test_data/exact_versions/datagen.py \
    --source /tmp/lance-exact-version-baseline
git worktree remove /tmp/lance-exact-version-baseline

Pass --write only when intentionally restoring these files from the locked baseline.

The compatibility tests require each stable writer to reproduce its fixture byte-for-byte and each reader to open and read the baseline file. The V2.0 standard fixture preserves footer (0, 3) while its self-described and mini-Lance fixtures preserve (2, 0). V2.3 is unstable, so it has deterministic current-revision tests instead of a checked-in compatibility fixture.

Regenerate these fixtures only from the baseline writer APIs. Files generated with the implementation under test are not independent compatibility evidence.