Support MCP's server.json and mcp.json import

goose has its own repository for MCP servers but given that there is an MCP server for everything now, this concept is outdated. goose has deeplinks to install remote MCP servers but uses its own format for that. Meanwhile the world has standardized around mcp.json as an unofficial standard, with [server.json](https://github.com/modelcontextprotocol/registry/blob/main/docs/reference/server-json/generic-server-json.md) as an official standard. We should [retire our registry](https://github.com/aaif-goose/goose/discussions/10830) and adopt that standard, support it through deeplinks, upload & paste. Integration with registries like Pulse should then be relatively easy and can be done as part of this or in a follow up.

The issue involves retiring the existing MCP server registry and integrating support for the standard server.json and mcp.json formats. Start by examining the current registry implementation and deeplink handling in the codebase. Understand how MCP servers are currently installed and configured. Then, implement parsing and validation for the new JSON standards, and update the deeplink, upload, and paste functionalities to use them. Testing should ensure backward compatibility is not broken for existing users.

Rédigé par le modèle d'indexation à partir du texte de l'issue.