Storing variables in a secure way

### Feature summary

Secure variables in mcp.json

### What problem are you trying to solve?

In VS Code we can store secrets as inputs, so they are not visible in plain text:
```
{
"servers": {
"mcp-with-secret": {
"url": "https://example.com/api",
"type": "http",
"headers": {
"Authorization": "Bearer ${input:pat}"
}
}
},
"inputs": [
{
"type": "promptString",
"id": "pat",
"description": "Enter your Personal Access Token (PAT)",
"password": true
}
]
}
```

Is it possible to make such functionality in this app?

### Proposed solution

_No response_

### Workflow impact

_No response_

### Installation context

_No response_

### Additional context

_No response_