## Thinking Path
> - Paperclip validates every change through an immutable reusable PR
workflow.
> - That caller still pinned a revision that ran pnpm setup before Node
setup.
> - The implementation fix in #12808 is therefore present on master but
inactive for ordinary PR CI.
> - Advancing the immutable caller pin activates the already tested
Node-first workflow.
> - A focused contract prevents the caller from silently returning to
the old revision.
> - The benefit is a faster PR feedback loop without changing product
code or secret boundaries.
## Linked Issues or Issue Description
Refs #12808
## What Changed
- Pin ordinary PR CI to trusted workflow revision
`a0a78ee60946a5f79f85b2bd0584fc766fae43bb`.
- Assert that the reusable workflow call is canonical, unique, and
SHA-pinned to that audited revision.
## Verification
- Focused workflow security test: 8/8.
- Prettier passed.
- Actionlint passed.
- `git diff --check` passed.
## Risks
Low risk. The change only advances an immutable reusable-workflow pin to
a revision whose full ordinary CI and security checks passed. Product
code and credentials are unchanged.
## Model Used
OpenAI Codex GPT-5 with agentic reasoning and repository tool use.
## Checklist
- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used
- [x] I have linked the related public PR
- [x] I have not referenced internal issue links
- [x] My branch name describes the change
- [x] I have run focused tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have considered and documented risks
89bf6a33c2