fix(cron): don't crash on cron list when a job's repeat is null

`cron_list` read `job.get("repeat", {})`, but the dict-default only
applies to a MISSING key. A one-shot job persisted with `"repeat": null`
returns None, and the next `.get("times")` raised AttributeError, taking
down the whole `cron list` output. Coalesce with `or {}` so a
present-but-null repeat renders as ∞ like the other cron readers already
do. Adds a regression test.

Co-authored-by: Teknium <127238744+teknium1@users.noreply.github.com>

hermes_cli/cron.py

@@ -81,7 +81,10 @@ def cron_list(show_all: bool = False):
         state = job.get("state", "scheduled" if job.get("enabled", True) else "paused")
         next_run = job.get("next_run_at", "?")
 
-        repeat_info = job.get("repeat", {})
+        # `repeat` may be present-but-null in the job record (e.g. a one-shot
+        # job persisted with "repeat": null), so coalesce to {} rather than
+        # relying on the dict-default, which only applies to a missing key.
+        repeat_info = job.get("repeat") or {}
         repeat_times = repeat_info.get("times")
         repeat_completed = repeat_info.get("completed", 0)
         repeat_str = f"{repeat_completed}/{repeat_times}" if repeat_times else "∞"