Update actions/checkout to v7

[EricWittmann]

Summary

• Update actions/checkout from v6 to v7

Context

This dependency upgrade was split from Renovate PR #26 for easier review and testing.

Test Plan

• Build passes
• Tests pass
• No breaking changes detected

[EricWittmann]

Review Summary

This PR updates actions/checkout from v6 (df4cb1c0...) to v7 (9c091bb2...) across all four GitHub Actions workflow files, as split out from Renovate PR #26.

Analysis

Changes reviewed:

• .github/workflows/npm-publish.yaml — 1 checkout reference updated
• .github/workflows/publish-docs.yml — 2 checkout references updated
• .github/workflows/release.yaml — 2 checkout references updated
• .github/workflows/verify.yaml — 1 checkout reference updated

All changes are consistent: every occurrence of the old v6 commit SHA is replaced with the new v7 commit SHA, and the version comments are updated accordingly (# v6 → # v7).

Good practices observed:

• ✅ Actions are pinned to full commit SHAs (not mutable tags), which is a supply-chain security best practice
• ✅ Human-readable version comments (# v7) are maintained alongside the SHA pins
• ✅ No workflow logic changes — purely a dependency version bump
• ✅ All instances across the repo are updated (no stale references left behind)

Findings

No issues found. This is a clean, minimal dependency upgrade with no functional or security concerns.

Overall Assessment

✅ Looks good to merge. Straightforward version bump applied consistently across all workflow files.