Normalize actions/checkout to a single major version (v4 vs v5 split)

[d-morrison]

Already resolved on main — closing.

The v4/v5 split this issue described no longer exists. Every actions/checkout reference in the repo is now uniformly pinned to a single major version:

actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0

across all workflows and composite actions (_selftest.yml, check-*, claude*.yml, cleanup-pr-previews.yml, preview-deploy.yml, quarto-publish.yml, slide-major-tag.yml, summary.yml, sync-shared-fragments.yml, bump-submodule.yml, preview/action.yml). Dependabot bumped the pins past v5 to v7.0.0 after this issue was filed, which incidentally collapsed the two majors into one.

No 34e114876b0b11c390a56381ad16ebd13914f8d5 (v4) or 93cb6efe18208431cddfb8368fd83d5badbf9bfd (v5) references remain, so there's nothing left to normalize.

[d-morrison]

Working on this --- paws off until I'm done.

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Generated by Claude Code

[d-morrison]

Stand down --- on closer look this is already resolved on main. Dependabot bumped every actions/checkout pin past v5 to a uniform @9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0, so the v4/v5 split no longer exists and there's nothing to normalize. No PR needed. (The only stray v4.3.1 left is a doc example in README.md, which is out of scope for this issue.)

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Generated by Claude Code