Constant PRODUCER_OFFSETS_TABLE 

pub const PRODUCER_OFFSETS_TABLE: &'static str;

The foreign-write dedup watermark (design 306): one row per producer, overwritten in place.

This is the same shape the write plane already uses for optimistic clients (CLIENT_MUTATIONS_TABLE) and for replication consumers (_rindle_source_offsets) — bounded by distinct producers, so there is nothing to reclaim and no TTL, sweep, or retention floor. Unlike the opaque key set it replaces, an absent row is not ambiguous: a watermark of 0 means “this producer has written nothing”, which the admission rule handles exactly like any other value. Rows are captured (registered for replication) so a journal restore brings the dedup state back with the effects it deduplicates — see design 306 §3.3.