fix(skills): resolve session resolution, add cancelled event status, and scope mqtt topic

.agents/skills/multi-agent-mux-stop/scripts/stop_session.sh

@@ -215,11 +215,12 @@ if [ "$PURGE" = "1" ] && [ "$HERDR_ALIVE" = "1" ]; then
     echo "  Refusing registry removal — records preserved (no state was modified)." >&2
     echo "  Diagnose the stuck TUI (herdr session attach '$SESSION_NAME'), then re-run" >&2
     echo "  stop_session.sh --purge-conversation --yes (retry is safe/idempotent)." >&2
-    delegate_publish_event "$DELEGATE_JOB_ID" error "purge aborted: herdr session still alive"
+    delegate_publish_event "$DELEGATE_JOB_ID" cancelled "purge aborted: session still alive; no state was modified"
     exit 4
   fi
 fi
 
+# INVARIANT: Terminal events for a job must be published AFTER atomic_dump_yaml updates the session status
 atomic_dump_yaml "$AGENT_SESSIONS_YAML" \
   SESSION_NAME="$SESSION_NAME" AGENT="$AGENT" PURGE="$PURGE" \
   NOW_ISO="$NOW_ISO" NOW_EPOCH="$NOW_EPOCH" LAST_STATUS="$LAST_STATUS" \
@@ -358,7 +359,7 @@ else:
     print(f"updated: {name} status={target['status']}", flush=True)
 PYEOF
 
-delegate_publish_event "$DELEGATE_JOB_ID" completed "session terminated"
+delegate_publish_event "$DELEGATE_JOB_ID" cancelled "session stopped by operator before job completion"
 
 echo
 echo "=== stop complete ==="