feat(casan): establish assurance kernel and harden control plane

packages/casan-harness/scripts/bash/agent-metrics.sh

@@ -110,6 +110,10 @@ LATENCY_MS=$((END_MS - START_MS))
 if [[ ! -f "$OUTPUT_FILE" ]]; then
   STATUS="failed"
   ERROR_MSG="${ERROR_MSG:-output file not produced}"
+  # A zero command exit does not make the step successful when the runtime
+  # contract requires an output artifact and none was produced. Telemetry can
+  # record this failure successfully, but must propagate a failed step outcome.
+  [[ "$EXIT_CODE" -eq 0 ]] && EXIT_CODE=1
   : > "$OUTPUT_FILE"
 fi