Found by a test of mine that asserted the union was closed and then failed:
TypeBox objects permit unknown properties by default, so a `start_print`
carrying an `ams_mapping` validated and the field was silently dropped.
Every command variant is now `additionalProperties: false`, and
`printer_telemetry` deliberately stays open. The asymmetry follows from who
writes each message. Telemetry comes from gateways in the field and is read
liberally: an unknown field must not cost a whole farm's batch, and a gateway
newer than the backend should still be understood. A command is written by
the backend, is four fields, and moves a physical machine - there an
unrecognised field is a bug on the sending side, and dropping it silently is
the worst outcome available, because a caller that misspells a field watches
its command succeed while the machine does something else.
`ams_mapping` is the case that matters: it is deliberately absent from
`start_print` because the gateway reads the mapping out of the project
archive, and a caller passing one has misunderstood something that previously
cost a heated nozzle and a self-paused print. It is now told so.
octoturge
99545703cb