Constant PUBLISH_UNRESOLVED_CODE 

pub const PUBLISH_UNRESOLVED_CODE: u16 = 0x0103;

The publish’s append outcome is not known: the server could not tell whether the row was stored.

Minted in the server-layer band (0x0100–0x01FF) as the next free value. It is distinct from every definite failure — neither a roster refusal nor the undifferentiated 0xFFFF — so a producer can tell by the code alone, never by the message text, that its publish is unresolved rather than refused, and retry with the same idempotency key instead of blindly.