mcp schema authority

this should be the Source of Truth. https://github.com/githubnext/gh-aw/blob/main/docs/public/schemas/mcp-gateway-config.schema.json

https://github.com/githubnext/gh-aw-mcpg/blob/main/internal/config/schemas/mcp-gateway-config.schema.json should refer to that one