Security: Harden GitHub Actions workflows

Hey, we found some CI/CD security issues in this repo's workflows using Runner Guard, our open-source CI/CD security scanner at Vigilant. These are the same vulnerability classes being actively exploited right now in the tj-actions, Trivy, LiteLLM supply chain attack chain. We scanned the top 50K repos on GitHub and over 20,000 have this same problem. We're trying to get fixes out to as many maintainers as possible before more repos get hit.

This PR fixes what we could automatically, and flags anything else that needs a manual look. There's a real person behind this PR, we're actively checking back on comments so if you have any questions just drop them here and we'll respond.

Fixes applied (in this PR)

Rule	Severity	File	Description
RGS-007	high	.github/workflows/ci.yml	Pinned 5 third-party action(s) to commit SHA
RGS-007	high	.github/workflows/compressed-size.yml	Pinned 2 third-party action(s) to commit SHA
RGS-007	high	.github/workflows/deploy-docs.yml	Pinned 1 third-party action(s) to commit SHA
RGS-007	high	.github/workflows/release-drafter.yml	Pinned 1 third-party action(s) to commit SHA
RGS-007	high	.github/workflows/release.yml	Pinned 2 third-party action(s) to commit SHA

Advisory: additional findings (manual review recommended)

No additional findings beyond the fixes applied above.

Why this matters

GitHub Actions workflows that use untrusted input in run: blocks, expose
secrets inline, or use unpinned third-party actions are vulnerable to
code injection, credential theft, and supply chain attacks. These are the same
vulnerability classes exploited in the tj-actions/changed-files incident
and subsequent supply chain attacks, which compromised CI secrets across
thousands of repositories.

How to verify

Review the diff — each change is mechanical and preserves workflow behavior:

• SHA pinning (RGS-007): Pins third-party actions to immutable commit SHAs
  (original version tag preserved as comment)

Run brew install Vigilant-LLC/tap/runner-guard && runner-guard scan . or install from the
repo to verify.

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Found by Runner Guard | Built by Vigilant Cyber Security | Learn more

If this PR is not welcome, just close it -- we won't send another.