ci: activate Node-first pnpm setup for PRs (#12810)

## 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

.github/workflows/pr.yml

@@ -10,4 +10,4 @@ permissions:
 
 jobs:
   ci:
-    uses: paperclipai/paperclip/.github/workflows/pr-trusted.yml@f038633bf5b04163ff985ef0542876bd9f455379
+    uses: paperclipai/paperclip/.github/workflows/pr-trusted.yml@a0a78ee60946a5f79f85b2bd0584fc766fae43bb

tests/runner-e2e/workflow-security.test.ts

@@ -3,6 +3,8 @@ import path from "node:path";
 import { describe, expect, it } from "vitest";
 
 const repositoryRoot = path.resolve(import.meta.dirname, "../..");
+const ordinaryPrTrustedWorkflowRevision =
+  "a0a78ee60946a5f79f85b2bd0584fc766fae43bb";
 const fullStackTestNeeds =
   /needs:\s*\[\s*authorize,\s*target_lock,\s*catalog,\s*daytona_image,\s*build_runner_artifacts,\s*build_remote_provider_pack,?\s*\]/u;
 const buildRunnerNeeds =
@@ -11,6 +13,26 @@ const buildRemoteProviderPackNeeds =
   /needs:\s*\[\s*authorize,\s*target_lock,\s*catalog,\s*daytona_image,\s*build_runner_artifacts,?\s*\]/u;
 
 describe("public repository paid workflow security", () => {
+  it("pins ordinary PR CI to the trusted Node-before-pnpm workflow", async () => {
+    const ordinaryPrWorkflow = await readFile(
+      path.join(repositoryRoot, ".github/workflows/pr.yml"),
+      "utf8",
+    );
+    const trustedWorkflowCalls = [
+      ...ordinaryPrWorkflow.matchAll(
+        /^\s+uses:\s+(paperclipai\/paperclip\/\.github\/workflows\/pr-trusted\.yml)@([0-9a-f]{40})$/gmu,
+      ),
+    ];
+
+    expect(trustedWorkflowCalls).toHaveLength(1);
+    expect(trustedWorkflowCalls[0]?.[1]).toBe(
+      "paperclipai/paperclip/.github/workflows/pr-trusted.yml",
+    );
+    expect(trustedWorkflowCalls[0]?.[2]).toBe(
+      ordinaryPrTrustedWorkflowRevision,
+    );
+  });
+
   it("keeps pnpm bootstrap registry telemetry out of trusted workflow setup", async () => {
     for (const workflowName of [
       "runner-full-stack-e2e.yml",