Add Claude Code GitHub Workflow - #1

Process completed with exit code 1.

Action failed with error: Claude Code is not installed on this repository. Please install the Claude Code GitHub App at https://github.com/apps/claude

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/