chore: fix zizmor findings in workflows

[ergousha]

Why zizmor?

zizmor is a static analysis tool for GitHub Actions workflows. It catches security misconfigurations that are easy to miss in code review but are commonly exploited in supply-chain attacks.

Findings addressed

unpinned-uses — Actions pinned to a tag (e.g. @v1) can silently change if the tag is force-pushed or hijacked. Pinning to an immutable commit SHA guarantees the exact code that ran in CI today is the same code that runs tomorrow, even if the upstream repo is compromised.

artipacked — By default actions/checkout persists a GitHub token in the local git config so that subsequent git commands can authenticate. If any later step in the job (or a transitive action) exfiltrates the workspace, it gets the token for free. Setting persist-credentials: false removes the token after checkout unless it is explicitly needed.

dependabot-cooldown — Without a cooldown, Dependabot can open PRs for a newly published package version within minutes of release. A short window is a known vector for dependency-confusion and typosquatting attacks where a malicious version is published and auto-merged before the community notices. Requiring a minimum 7-day cooldown gives the ecosystem time to vet new releases.

Validation

zizmor --min-severity low .github/
No findings to report. Good job! (32 suppressed)

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