An inbound forward is shown as one rather than as the sender's own
words. Both flag shapes accepted, like ctl: org.json's optBoolean does
not coerce a number, so an engine reading one shape would silently miss
every forward the other two send.
⚠️ The subtle one: Content.text returns raw bytes with no envelope at
all when there is no id, reply or link to carry. A forward that was not
counted in that condition would lose its flag and arrive looking like
the sender's own composition — so is part of the test for
whether an envelope is needed, not just a field inside it.
Codec only. Originating a forward needs the transcript work in #10.
Refs paulhitt/flamenet-messenger-ios#28
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
