Bug Description

Cron tasks that are currently running are incorrectly marked as `lost` after a Gateway restart.

Root Cause

The active job tracking mechanism uses an in-memory `Set` (`activeJobIds`) that is not persisted across restarts.

Code flow:

1. When a cron job starts running, markCronJobActive(jobId) adds the job ID to a memory-only Set
2. Gateway restarts → the Set is cleared
3. After the sweeper grace period (5 minutes), isCronJobActive() returns `false`
4. Task is marked as `lost` with error: "backing session missing"

Key files:

• `task-registry.maintenance-D1dTWf8y.js` — `CRON_ACTIVE_JOB_STATE_KEY` singleton stores only in-memory `activeJobIds` Set
• `server.impl-BbJvXoPb.js` — calls `markCronJobActive`/clearCronJobActive but state is never persisted

Impact

• Any long-running cron task (>5 min) will be marked `lost` if Gateway restarts during execution
• `cron restart gateway` workflow breaks running jobs
• Config changes requiring Gateway restart disrupt in-flight tasks

Proposed Fix

Persist `activeJobIds` to the cron store file (`~/.openclaw/cron/jobs.json`).

Implementation approach:

1. Store shape change — add `activeJobIds: string[]` field to the cron store JSON:
   ```json
   {
   "version": 1,
   "jobs": [...],
   "activeJobIds": ["job-id-1", "job-id-2"]
   }
   ```

2. In `server.impl-BbJvXoPb.js`:

   • `markCronJobActive(jobId)` → push to `state.store.activeJobIds` + `persist(state)`
   • `clearCronJobActive(jobId)` → filter from `state.store.activeJobIds` + `persist(state)`
   • `ensureLoaded()` → on startup, for any job with `job.state.runningAtMs` set, call `markCronJobActive(job.id)` to rebuild the in-memory Set

3. In `store-0nH_zmSJ.js`:

   • `loadCronStore()` → load and hydrate `activeJobIds` from file
   • `saveCronStore()` → persist `activeJobIds` alongside jobs

This approach leverages the existing `persist()` mechanism and the already-persisted `job.state.runningAtMs` field to determine which jobs were running at restart time.

Workaround

None — this is a design gap in the persistence layer.

Environment

• OpenClaw version: 2026.4.2+
• Gateway running as launchd/systemd service
• Any cron job with execution time > 5 minutes