openapi2mcp: generated config.tools entries omit the responses field from the OpenAPI spec

Summary
When converting an OpenAPI spec to MCP configuration (via deck file openapi2mcp, which calls openapi2mcp.Convert), each generated tool under config.tools includes the operation's request contract but not the operation's responses. The OpenAPI responses object is never read during conversion.

Current behavior
operation.Parameters and operation.RequestBody are consumed, but operation.Responses is never accessed anywhere in the package. There is no responses (or equivalent) key in the tool map and no builder function for it.

Expected / desired behavior

Generated tool entries should optionally include response schema information derived from the OpenAPI responses object (e.g. a responses field keyed by status code, each with its media-type content schemas, mirroring the shape of request_body).

Start at the deck file openapi2mcp entry point and follow its call to openapi2mcp.Convert, comparing how operation.Parameters and operation.RequestBody are converted. Trace the operation.Responses data and define the generated responses shape with status codes and media-type content schemas; done means config.tools entries preserve that response information when present.

Written by the indexing model from the issue text.