Soul pass on 66e6fe8: document and fixture the read form of
fork_too_large (live on main; CultLib limitation 13 is stale), the
ResponseTooLarge 503 and a unit-variant Refused; say that only operation
messages have sorted keys, what failure diagnostics and the schema
catalog reply are, where forks come from, and that the listing gate is
not live (no receiver on a Mind with private questions before
cut-desk-feed-listing). Fixtures use a held fork id, synthetic record.
.gitattributes keeps .bin/.msgpack binary and .hex LF.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>