_unservable_put sized a put by building the envelope it would store, and
that read document["recordKey"] and document["payload"] directly: a put
over RUDP with no recordKey raised KeyError out of the RUDP loop and
ended the thread for every peer. A string payload raised TypeError the
same way.
_unservable_put now refuses a put whose document lacks a string recordKey
or a binary payload as malformed_document_put, the code the server
already uses for a put with no document map, before any sizing reads it
and before its early return, so the TCP path refuses it too instead of
raising in apply_raw_put_message.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>