fix: install js-yaml dependency for CI workflow validation

actions/github-script@v7 does not bundle js-yaml, causing the
validate job to fail with "Cannot find module 'js-yaml'".

Author: chriswydra

.github/workflows/ci.yml

@@ -15,6 +15,9 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Install js-yaml
+        run: npm install js-yaml
+
       - name: Validate workflow syntax
         uses: actions/github-script@v7
         with: