SessionProjectionHints gains a required `kind`: `sequenced` when the Host's live registry computed the block for an attached Session, `cached` when a header-only listing viewed it from the persisted projection cache. `asOfSeq` stays the producer's own watermark in that space, so the cache read faces report the lowest served row seq again instead of the -1 sentinel. The two fields are independent: `kind` names the sequence space, `asOfSeq` the position in it.