[Bug]: Improve error message for malformed blueprint JSON

[devi5040]

Describe the bug

When a blueprint JSON file contains invalid syntax or is malformed, Scaffinity currently surfaces the raw JSON.parse error.

While technically correct, the message isn't very user-friendly and doesn't clearly indicate which blueprint caused the issue or provide guidance for fixing it.

Blueprint or command used

{
  "name": "example",
  "files": [
    {
      "path": "README.md",
      "content": "Hello"
    }
  ] // missing closing brace

scaffinity generate blueprint.json

Expected behavior

Scaffinity should catch JSON parsing errors and display a clearer, more actionable error message.

For example:

• The blueprint file that failed to parse.
• The approximate line/column where parsing failed.
• A suggestion to validate the JSON syntax before retrying.

Actual behavior

The CLI prints the raw JSON.parse error, which may be difficult for beginners to understand.

Environment

• Scaffinity version: scaffinity -v
• Node version: node -v
• OS:
• Package manager: npm / pnpm / yarn

Additional context

Improving this error message would make the CLI more beginner-friendly and provide a better developer experience when authoring custom blueprints.