InstallSnapshotTermOutOfRange

RaftEngine.snapshotChunkRefusal bound 2 (#1868): an InstallSnapshot whose lastIncludedTerm is outside 0..min(term, MAX_PLAUSIBLE_TERM).

A snapshot's lastIncludedTerm is the term of a log entry the sender held, and a node's log never carries a term above its own currentTerm — which the frame states as term. So lastIncludedTerm <= term is checkable from the frame alone, the identical §5.3 argument AppendEntriesEntryTermOutOfRange makes on its own lane. The MAX_PLAUSIBLE_TERM ceiling is folded into the same bound and enforced here rather than inherited, which is what makes the check survive #1897 unchanged. Two arms under one gate, as at AppendEntriesPrevLogIndexOutOfRange.