PHASE 1 – FILEPLAN (JSON ONLY): Return a JSON object with key 'files' listing all files to create.
Each entry: {path: string (relative to project_dir), purpose: string}. No code blocks.

CRITICAL INSTRUCTIONS FOR OPEN MODELS:
- Respond ONLY with valid JSON
- NO markdown formatting
- NO code blocks (```json or ```)
- NO explanatory text before or after
- NO comments in JSON
- Start directly with { and end with }
- Use double quotes for all strings
- Ensure proper JSON syntax

EXAMPLE FORMAT:
{
  "files": [
    {
      "path": "README.md",
      "purpose": "Project documentation and setup instructions"
    },
    {
      "path": "app.py", 
      "purpose": "Main application entry point"
    }
  ]
}

