The transport schema requires both `code` and `description`, but the tool
description and both SDK instruction flavors described the call as passing a
program. `description` was reachable only through the parameter schema, so a
model following the prose emitted `{code}` alone and lost the whole written
program to an INVALID_ARGS rejection.
The length and format guidance stays in RUN_CODE_DESCRIPTION_PARAM_DESCRIPTION
alone, so the schema and the prompt cannot drift.
Fixes#2426
Yichen Jiang
63fecf2534