- Add GraphPseudoRole type ($END | $SUSPEND) to workflow-protocol
- Add 'suspended' to ThreadStatus
- evaluate() returns EvaluateSuspendResult for $SUSPEND targets
- Thread show/list derive suspended status from moderator evaluation
- validate-semantic treats $SUSPEND like $END (valid target, no outgoing edges)
- Tests: routing to $SUSPEND, mustache rendering, thread status display
Closes#588