fix(cron): classify denied isolated runs

docs/cli/cron.md

@@ -57,6 +57,11 @@ Note: if an isolated cron run returns only the silent token (`NO_REPLY` /
 `no_reply`), cron suppresses direct outbound delivery and the fallback queued
 summary path as well, so nothing is posted back to chat.
 
+Note: isolated cron runs treat known denial markers in final output, such as
+`SYSTEM_RUN_DENIED`, `INVALID_REQUEST`, and approval-binding refusal phrases, as
+errors. `cron list` and run history then surface the matched token in the error
+reason instead of reporting a blocked command as `ok`.
+
 Note: `cron add|edit --model ...` uses that selected allowed model for the job.
 If the model is not allowed, cron warns and falls back to the job's agent/default
 model selection instead. Configured fallback chains still apply, but a plain