Pin Claude Code Action to Sonnet 5

Keeps routine @claude reviews on the cheaper Sonnet tier instead of the
actions default model, for cost control.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: iruvan

.github/workflows/claude.yml

@@ -33,3 +33,4 @@ jobs:
         uses: anthropics/claude-code-action@v1
         with:
           anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
+          model: claude-sonnet-5