RhtNode

A tombstone charges its key only (#1392). The value it still carries is dead weight — nothing reads it, Rht.has/Rht.toJson/Rht.toXml all gate on isRemoved — and charging it made the running docSize disagree with a rebuild of the same document, which replays the same removals. The value is left on the node rather than cleared so that what this SDK stores and serializes for a tombstone is byte-for-byte what it was, and what a peer sends us is kept verbatim: the convergence fix belongs in the accounting, not the wire format.