Long coding agent problem statement results in unrecoverable error (Truncate coding agent problem_statement)

Server-side behavior change now enforces a 30_000 character problem statement limit. Previously, the server would silently truncate.

This was an oversight from us that we do not cap the size of the payload, which can feasibly surpass that value.

Reports suggest that some users are hitting this issue, resulting in an unrecoverable error. The server-side team is not rolling back the change.