fix(types): compare and hash intervals by PostgreSQL duration

[dipeshbabu]

Cross-shard interval comparisons use individual fields, so 1 mon sorts after 31 days and equivalent values such as 1 day and 24 hours form separate groups. This also produces incorrect MIN/MAX results.

Use one allocation-free i128 duration for ordering, equality, and hashing, matching PostgreSQL's 30-day months and 24-hour days without overflowing the interval range.

Regression tests cover equivalent values, mixed signs, extreme ranges, and multi-shard ordering/grouping/min/max in text and binary formats.

Validation: all 27 jobs pass in CI, including strict formatting/Clippy, unit/doc tests, Linux/macOS builds, and all 21 integration suites on PostgreSQL 18.

[levkk]

Awesome. Do you want to try stacking the PRs? You basically change the base branch of this PR to your other PR, and GitHub can convert to a stack we can merge together!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[dipeshbabu]

Thanks! I checked, but GitHub currently doesn't support cross-fork stacks. Both PRs come from my fork, and I have read-only access upstream.

This branch already builds directly on #1558, with the interval fix isolated in e261e96d. The available path is to merge #1558 first, then rebase this PR onto main if needed.

[levkk]

Ah!! That's unfortunate! Okay, let's merge the CI fix first, then let's do the other ones one at a time. Please make sure to sign our CLA; without it, we can't accept contributions. Cheers!

#1560 (comment)

[dipeshbabu]

The CLA is signed, and its checks are now green on #1558 and #1560. All three PRs' code checks pass. Agreed on merging #1558 first, followed by #1559 and #1560 one at a time.

[dipeshbabu]

Rebased onto main after #1558 merged. This PR now contains only the interval fix. All 27 validation jobs pass.