fix: cron scheduler crash on string schedule formats

The scheduler crashed with AttributeError: 'str' object has no
attribute 'get' because jobs.json stores schedules as strings
(e.g. '*/3 * * * *', 'every 15m') but downstream functions expect
dicts with a 'kind' key.

Added _normalize_job_schedules() that runs on load_jobs() to parse
all string schedules into structured dicts. Also added defensive
isinstance checks at two call sites.

Fixes the frozen scheduler — all cron jobs were stuck since April 13.

cron/jobs.py

@@ -317,6 +317,21 @@ def compute_next_run(schedule: Dict[str, Any], last_run_at: Optional[str] = None
 # Job CRUD Operations
 # =============================================================================
 
+def _normalize_job_schedules(jobs: List[Dict[str, Any]]):
+    """Convert any string schedules to parsed dicts in-place."""
+    for job in jobs:
+        sched = job.get("schedule")
+        if isinstance(sched, str):
+            try:
+                job["schedule"] = parse_schedule(sched)
+            except Exception:
+                job["schedule"] = {"kind": "unknown", "raw": sched}
+        elif isinstance(sched, dict):
+            pass  # already fine
+        elif sched is None:
+            pass  # no schedule (cron-managed or paused)
+
+
 def load_jobs() -> List[Dict[str, Any]]:
     """Load all jobs from storage."""
     ensure_dirs()
@@ -326,13 +341,16 @@ def load_jobs() -> List[Dict[str, Any]]:
     try:
         with open(JOBS_FILE, 'r', encoding='utf-8') as f:
             data = json.load(f)
-            return data.get("jobs", [])
+            jobs = data.get("jobs", [])
+            _normalize_job_schedules(jobs)
+            return jobs
     except json.JSONDecodeError:
         # Retry with strict=False to handle bare control chars in string values
         try:
             with open(JOBS_FILE, 'r', encoding='utf-8') as f:
                 data = json.loads(f.read(), strict=False)
                 jobs = data.get("jobs", [])
+                _normalize_job_schedules(jobs)
                 if jobs:
                     # Auto-repair: rewrite with proper escaping
                     save_jobs(jobs)
@@ -642,7 +660,13 @@ def advance_next_run(job_id: str) -> bool:
     jobs = load_jobs()
     for job in jobs:
         if job["id"] == job_id:
-            kind = job.get("schedule", {}).get("kind")
+            schedule = job.get("schedule", {})
+            if isinstance(schedule, str):
+                try:
+                    schedule = parse_schedule(schedule)
+                except Exception:
+                    return False
+            kind = schedule.get("kind")
             if kind not in ("cron", "interval"):
                 return False
             now = _hermes_now().isoformat()
@@ -699,6 +723,11 @@ def get_due_jobs() -> List[Dict[str, Any]]:
         next_run_dt = _ensure_aware(datetime.fromisoformat(next_run))
         if next_run_dt <= now:
             schedule = job.get("schedule", {})
+            if isinstance(schedule, str):
+                try:
+                    schedule = parse_schedule(schedule)
+                except Exception:
+                    schedule = {"kind": "unknown"}
             kind = schedule.get("kind")
 
             # For recurring jobs, check if the scheduled time is stale