fix(cron): share isolated announce flow + harden cron scheduling/delivery (#11641)

* fix(cron): comprehensive cron scheduling and delivery fixes

- Fix delivery target resolution for isolated agent cron jobs
- Improve schedule parsing and validation
- Add job retry logic and error handling
- Enhance cron ops with better state management
- Add timer improvements for more reliable cron execution
- Add cron event type to protocol schema
- Support cron events in heartbeat runner (skip empty-heartbeat check,
  use dedicated CRON_EVENT_PROMPT for relay)

* fix: remove cron debug test and add changelog/docs notes (#11641) (thanks @tyler6204)

CHANGELOG.md

@@ -10,6 +10,7 @@ Docs: https://docs.openclaw.ai
 
 ### Fixes
 
+- Cron: route text-only isolated agent announces through the shared subagent announce flow; add exponential backoff for repeated errors; preserve future `nextRunAtMs` on restart; include current-boundary schedule matches; prevent stale threadId reuse across targets; and add per-job execution timeout. (#11641) Thanks @tyler6204.
 - Agents: recover from context overflow caused by oversized tool results (pre-emptive capping + fallback truncation). (#11579) Thanks @tyler6204.
 - Gateway/CLI: when `gateway.bind=lan`, use a LAN IP for probe URLs and Control UI links. (#11448) Thanks @AnonO6.
 - Memory: set Voyage embeddings `input_type` for improved retrieval. (#10818) Thanks @mcinteerj.