fix: ensure manifest timestamp is monotonically increasing

[jackye1995]

No description provided.

[github-actions]

Code Review

P1: Potential overflow in timestamp computation

In temporal.rs:50, the expression prev + MILLIS_TO_NANOS could theoretically overflow if prev is close to u128::MAX. While this is extremely unlikely in practice (timestamps are bounded to ~10^19 nanos currently), adding a saturating add or a checked add with fallback would be more defensive:

match prev_timestamp_nanos {
    Some(prev) => std::cmp::max(current_nanos, prev.saturating_add(MILLIS_TO_NANOS)),
    None => current_nanos,
}

---

Minor observations (non-blocking):

1. The documentation states "at least 1 millisecond" but the code actually enforces "exactly 1 millisecond" as the minimum increment. This is fine but worth noting for precision.

2. Consider adding an integration-style test that actually commits multiple versions in rapid succession and verifies the timestamps are monotonically increasing end-to-end.

Overall, the change is well-structured with good test coverage and clear documentation.

[codecov]

Codecov Report

❌ Patch coverage is 97.43590% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
rust/lance/src/io/commit.rs	66.66%	1 Missing ⚠️

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