generator: include errordetails in error

[birdayz]

previously we provided only code and message.

e.g. when using claude code as client: Violation error in e.g. dataplane API of redpanda cloud:

Old:

MCP error -32603: invalid_argument: provided parameters are invalid

New:

Error: {"code":"INVALID_ARGUMENT", "message":"provided parameters are invalid", "details":[{"@type":"google.rpc.ErrorInfo", "reason":"REASON_INVALID_INPUT", "domain":"redpanda.com/dataplane"}, 
     {"@type":"google.rpc.BadRequest", "fieldViolations":[{"field":"topic.name", "description":"value does not match regex pattern `^[a-zA-Z0-9._\\-]*$`"}]}]}