FLX-3301: emit writer used out of order

Family: seam/conformance (the 3000 band)

A stream is opened once, written to zero or more times, and closed once. Writing before the header is opened, writing after the stream is closed, or opening twice would put rows outside the framing the outputDigest covers (KERNEL-SPEC §8), so the writer refuses rather than digesting a stream whose shape nobody declared.

Look it up offline

$ fluxsim explain FLX-3301

Every code is listed in the error index.