Add command to print simplified visualization of schemas

[just-be-dev]

Pulled out of #78

This PR adds a printer and debug command to the generation setup. You can use mise run print-schema to invoke it or mise run print-schema WebViewOptions to print a single schema.

The output looks like this

Response
│   description: Responses from the webview to the client.
└── discriminated-union (by $type)
    ├── ack
    │   └── id: string
    ├── result
    │   ├── id: string
    │   └── result: ResultType
    └── err
        ├── id: string
        └── message: string