pub const RDONE: u8 = 8; // 8u8Expand description
r[impl jetstream.subscription.compat]
The terminator, and cancellation, take global message ids in the
space below MESSAGE_ID_START, exactly as RJETSTREAMERROR already
does. That is what keeps 102 + 2 * index intact: a streaming method
costs no extra per-method id, so r[jetstream.rpc.swift.message-ids]
and r[jetstream.rpc.ts.message-ids] do not change and no protocol is
re-generated for its unary methods.
5, 6, 7 and 11 are taken by the error frames; 100 and 101 by version.
RERROR is the last of those: it sat at 107, overlapping the
generated response id for method index 2, until it moved down here to
join its siblings.