Reduce code review effort by automating mechanical checks

@wuw92 is already working on this.

Since Sep 14, 2026.

Inspired by #1318, I reviewed three months of historical DiskANN PR comments to identify rules that could be checked mechanically.

The goal is to reduce repetitive review effort by adding or improving CI/lint checks for suitable rules, so reviewers can focus on correctness and design. Some candidates may need a new check; others may only need better coverage from existing tools.

The checklist below tracks the candidate rules identified from that review.

- [x] **Rustdoc links:** catch broken internal links in Rust documentation through CI. (#1400)
- [x] **License headers:** catch missing or nonstandard license headers in Rust source files through CI. (#1401)
- [ ] **SAFETY comments:** consistent documentation-presence checks for unsafe code.
- [x] **Dependency versions:** avoid unnecessary duplicate versions. (#1410: workspace direct dependencies only; transitive-only duplicates are out of scope.)
- [x] **Lint suppressions:** use `#[expect(...)]` to detect suppressions that are no longer needed. (#1409)

Supporting references

- **Rustdoc links:** [maintainer request](https://github.com/microsoft/DiskANN/pull/1318#discussion_r3770946930).
- **License headers:** [maintainer's scope clarification](https://github.com/microsoft/DiskANN/pull/1318#discussion_r3759006941), [related discussion](https://github.com/microsoft/DiskANN/pull/1338#discussion_r3787153897).
- **SAFETY comments:** [discussion](https://github.com/microsoft/DiskANN/pull/1318#discussion_r3761640292), [presence versus correctness](https://github.com/microsoft/DiskANN/pull/1315#discussion_r3730664750).
- **Dependency versions:** [maintainer request](https://github.com/microsoft/DiskANN/pull/1205#discussion_r3492804509), [transitive-dependency discussion](https://github.com/microsoft/DiskANN/pull/1205#discussion_r3492820848), [follow-up](https://github.com/microsoft/DiskANN/pull/1205#discussion_r3495015568).