Schema snapshot response format is missing data wrapper

The schema snapshot endpoint returns the schema wrapped in a `data` property, consistent with most other data endpoints. However, the OpenAPI specification currently describes the schema as being returned at the top level and does not reflect this `data` wrapper.

https://github.com/directus/openapi/blob/main/openapi/paths/schema/snapshot/schemaSnapshot.yaml#L14

Open openapi/paths/schema/snapshot/schemaSnapshot.yaml at the referenced response definition and compare it with other data endpoints that use a data wrapper. Update the schema snapshot response description to show the wrapper, then verify the OpenAPI document remains valid and the response shape matches the endpoint.

Written by the indexing model from the issue text.