chore: pin GitHub Actions to full-length commit SHAs

[joshuarli]

Summary

• Pin all GitHub Actions references in .github/ workflow files to full-length commit SHAs

Generated by devenv pin_gha.

🤖 Generated with Claude Code

[github-actions]

Semver Impact of This PR

🟢 Patch (bug fixes)

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Internal Changes

• (agents) Convert commands to dotagents skills by chargome in #1236

• Pin GitHub Actions to full-length commit SHAs by joshuarli in #1244

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