Gate external PRs on an assigned, linked issue (#3291)

Signed-off-by: Max Isbey <224885523+maxisbey@users.noreply.github.com>

.github/workflows/shared.yml

@@ -41,6 +41,12 @@ jobs:
         with:
           extra_args: --all-files --verbose
 
+      - uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6.4.0
+        with:
+          node-version: 24 # match the runtime actions/github-script@v8 uses
+      - name: PR intake gate scenarios
+        run: node --test .github/scripts/pr_intake_gate.test.js
+
       - name: Surface types match vendored schema
         run: |
           uv sync --group codegen --frozen