Two small, focused fixes for the cron scheduler and checkpoint manager.
1. _summarize_cron_failure_for_delivery (cron/scheduler.py):
Replaces the raw error dump in _process_job with a compact
pattern-matched summary. Provider rate limits, timeouts, and
authentication errors now produce a short human-readable message
instead of dumping multi-KB provider JSON into the delivery channel.
2. _repair_bare_repo_dirs (tools/checkpoint_manager.py):
Recreates refs/heads/ and branches/ directories after git gc
--prune=now, which can remove empty dirs from bare repos and cause
subsequent git add -A to fail with 'fatal: not a git repository'.
Called after all four git gc call sites.
Both fixes use only standard library imports and plug into existing
call sites with no architectural changes.
a5e06078b2