Support for ${input:name} in mcp.json

[tmnd1991]

Describe the bug

Now that the cli supports loading mcp server configuration from .vscode/mcp.json it's a problem it does not support asking for inputs. It makes the feature kind of useless because now I have to commit my secrets if I want to share the server configurations with my colleagues.

Affected version

GitHub Copilot CLI 0.0.421. Run 'copilot update' to check for updates.

Steps to reproduce the behavior

Start copilot in a folder with a mcp-json with ${input:____}.
Example:

{
	"servers": {
		"context7": {
			"type": "http",
			"url": "https://mcp.context7.com/mcp",
			"headers": {
				"CONTEXT7_API_KEY": "${input:context7_api_key}"
			}
		},
	},
	"inputs": [
		{
			"id": "context7_api_key",
			"type": "promptString",
			"description": "api key",
			"password": true
		}
	]
}

Expected behavior

Ask the user for input or look for a separate file containing secrets

Additional context

No response