The getAgents() function was recalculating nextRun to future dates when
it found past values. This prevented the cron scheduler from ever
finding due agents (nextRun <= now was always false since getAgents
had already pushed it to the future).
Also fix toast polling: use null sentinel for agents without initial
actions so first execution is still detected. Limit cron to 3 agents
per cycle and add logging.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>