Keep the stream side owned here: line bounds, the leading-brace check,
the write-queue limit and closure. On the birpc side, drop the strict
envelope validation, falsy-rejection normalization and fatal UTF-8
decoding. Calls to methods an endpoint does not own are answered with
birpc's error and unknown messages are ignored; the resolver still runs
only own methods and none after the endpoint closes.
One pipe delivers each evaluation's messages before its result, and the
child refuses calls from finished evaluations, so the per-message
evaluation id protected nothing. Remove it with the checks, counters and
helpers it required, measure outgoing messages only when posting, and
replace rethrowing validation blocks with early refusals.
Replace the length-prefixed JsonChannel and hand-written request/reply
correlation with typed birpc methods over newline-delimited JSON. The
host calls the child's run(); bindings call the host's invoke(); logs
and output-limit reports are notifications. The transport bounds
incoming lines and queued writes, validates UTF-8 and exposed methods,
and rejects outstanding calls when the pipe closes.
Drop logic made obsolete by the new transport, including the 32-bit
frame-length bound on maxMessageBytes.
_Kerman