[ENH](wal3): Trim body metadata

[domenkozar]

Summary

• disable Parquet statistics for the opaque wal3 body column
• retain statistics for offsets and timestamps
• add a large incompressible-record regression test covering fragment size, round-trip decoding, and setsum verification

Parquet's page-statistics default copies a single large binary value into min/max metadata multiple times. A focused probe reduced a roughly 2 MB one-record fragment from 10.24 MB to 2.05 MB. Existing fragments remain readable because this changes writer properties only.

S3 request count is unchanged, while fragment storage and transfer bytes drop substantially for large records.

Tests

• cargo test --manifest-path rust/wal3/Cargo.toml --lib writer::tests
• cargo test --manifest-path rust/wal3/Cargo.toml --lib interfaces::tests::checksum_parquet
• cargo clippy --manifest-path rust/wal3/Cargo.toml --lib -- -D warnings
• cargo fmt --manifest-path rust/wal3/Cargo.toml -- --check

Tilt-backed integration tests were not validated locally because the required services were not active.

[claude]

Claude Code Review

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[github-actions]

Reviewer Checklist

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Testing, Bugs, Errors, Logs, Documentation

• Can you think of any use case in which the code does not behave as intended? Have they been tested?
• Can you think of any inputs or external events that could break the code? Is user input validated and safe? Have they been tested?
• If appropriate, are there adequate property based tests?
• If appropriate, are there adequate unit tests?
• Should any logging, debugging, tracing information be added or removed?
• Are error messages user-friendly?
• Have all documentation changes needed been made?
• Have all non-obvious changes been commented?

System Compatibility

• Are there any potential impacts on other parts of the system or backward compatibility?
• Does this change intersect with any items on our roadmap, and if so, is there a plan for fitting them together?

Quality

• Is this code of a unexpectedly high quality (Readability, Modularity, Intuitiveness)

[domenkozar]

cc @rescrv