Implemented proto::ChainVerifier as a pure line-holding state machine:
each line is judged only once the next has arrived, so a Recovery record
can mark the line before it not-a-record. Adds ChainFailure, TornTail,
ChainReport, Location and ChainVerifier, wired through lib.rs and the
matching re-export in audit.rs. 13 chain tests pass; make gate prints
gate: ok.
Implemented-By: OpenCode session (model recorded in docs/implementer-log.md)
