chore: Update GitHub Actions to latest versions

- actions/checkout: v4.2.2 → v6.0.1 (8e8c483db84b4bee98b60c0593521ed34d9990e8)
- actions/setup-node: v4.1.0 → v6.1.0 (395ad3262231945c25e8478fd5baf05154b1d79f)

Pinned to commit SHAs for security best practices.

Author: jdalton

.github/workflows/claude-auto-review.yml

@@ -65,7 +65,7 @@ jobs:
           persist-credentials: false
 
       - name: Setup Node.js
-        uses: actions/setup-node@39370e3970a6d050c480ffad4ff0ed4d3fdee5af # v4.1.0
+        uses: actions/setup-node@395ad3262231945c25e8478fd5baf05154b1d79f # v6.1.0
         with:
           node-version-file: .node-version
 

.github/workflows/claude.yml

@@ -46,7 +46,7 @@ jobs:
           persist-credentials: false
 
       - name: Setup Node.js
-        uses: actions/setup-node@39370e3970a6d050c480ffad4ff0ed4d3fdee5af # v4.1.0
+        uses: actions/setup-node@395ad3262231945c25e8478fd5baf05154b1d79f # v6.1.0
         with:
           node-version-file: .node-version