Fix quorum attribute to use actual validator quorum instead of proposer
count, add missing ConsensusState::Expired handling in haveConsensus()
span, move ConsensusSpanNames.h to xrpld/consensus/ to resolve
levelization cycle, remove unused constants, enrich proposal receive
span with sequence, and correct stale documentation references.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>