Cross-validates the GEM 300 streams secsgem-py 0.3.0 doesn't ship
(S3 carriers, S14 control jobs, S16 process jobs) by minting custom
`SecsStreamFunction` subclasses on the fly and registering the
matching `DataItem` definitions (CARRIERID, CTLJOBID, PRJOBID, PRCMD,
CTLJOBCMD, MF, …) with `secsgem.secs.data_items`.
Drives the C++ passive server through:
* S3F17/F18 (E87 carrier action) — server replies CarrierIDUnknown
for the unregistered carrier.
* S16F5/F6 (E40 PRJobCommand) — server returns InvalidObject
for the nonexistent PJ.
* S16F27/F28 (E94 CJobCommand) — server cascades CJSTART.
Scope cut: S16F11 full-body and S14F9 (both have variable-length
nested lists with named scalar elements) hit a quirk of secsgem-py's
SFDL tokenizer where `< L name > <SCALAR> >` parses as a fixed-1
list, not a variable-length list of SCALARs. The full-body S16F11
is already round-tripped by the C++ unit tests (and via secsgem-py's
host driver in `host_vs_cpp_server.py`), so the raw harness focuses
on the no-variable-list messages where the SFDL grammar cooperates.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
