ci: check marketplace workflow access

Author: magisk317

.github/workflows/release.yml

@@ -58,6 +58,25 @@ jobs:
               }
             }
             core.setFailed('marketplace fork not ready');
+      - if: ${{ env.MARKETPLACE_PR_TOKEN != '' }}
+        name: Check marketplace workflow access
+        uses: actions/github-script@v7
+        with:
+          github-token: ${{ env.MARKETPLACE_PR_TOKEN }}
+          script: |
+            const forkOwner = context.actor;
+            const repo = 'marketplace';
+            const path = '.github/workflows/validate-pr.yml';
+            try {
+              await github.rest.repos.getContent({ owner: forkOwner, repo, path });
+              return;
+            } catch (error) {
+              if (error.status === 404) {
+                core.setFailed('Marketplace fork missing .github/workflows/validate-pr.yml. Sync the fork or use a token with workflow scope to allow pushing workflow files.');
+                return;
+              }
+              throw error;
+            }
       - if: ${{ env.MARKETPLACE_PR_TOKEN != '' }}
         uses: actions/checkout@v4
         with: