chore: pin GitHub Actions to commit SHAs (#557)

* chore: pin setup-python to immutable SHA

* fix: resolve package.json merge conflict (keep oxlint/oxfmt)

* chore: pin GitHub Actions to commit SHAs

Pin actions to specific commits for security and reproducibility:
- actions/checkout@v6: de0fac2
- actions/upload-artifact@v4: 043fb46

* chore: pin GitHub Actions to commit SHAs

- Pin actions/checkout, setup-node, upload-artifact, download-artifact
- Ensures reproducible and secure CI runs

* chore: pin GitHub Actions

* chore: pin all GitHub Actions to commit SHAs

Pins all GitHub Actions to immutable commit SHAs.

* chore: pin GitHub Actions to commit SHAs

* chore: pin all GitHub Actions to commit SHAs

- Pin actions/checkout, setup-python, setup-node, etc.
- Ensures reproducible and secure CI runs

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Co-authored-by: Codex <noreply@openai.com>

Author: KooshaPari