feat(crons): use max_runtime — immediate alert on error status + in_progress timeout #367

Summary

max_runtime from monitor_config is parsed but unused: a job stuck in_progress or ending error is only caught by schedule+margin staleness, not flagged earlier.

Why

Catching hung/failed runs earlier is the point of crons monitoring. Feature gap identified in #364 security review.

Acceptance criteria

• Monitor with status error alerts immediately (not waiting for schedule window)
• in_progress exceeding max_runtime flips to a timed-out/missed state and alerts
• Tests for both paths