chore(deps): update actions/setup-node action to v6

Author: renovate[bot]

.github/workflows/claude-md-maintenance.yml

@@ -23,7 +23,7 @@ jobs:
           fetch-depth: 0
 
       - name: Set up Node.js
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v6
         with:
           node-version: "20"