Scheduled cron jobs now pass the cron key into the send path, apply a
deterministic [0, N) second delay from scheduled_message_max_stagger_seconds
(default 1.5), and call send_channel_message with skip_user_rate_limit=True
so simultaneous jobs are not dropped by rate_limit_seconds. Per-channel and
bot_tx limits still apply. Document the new Bot key in config.ini.example;
tests assert kwargs, skip flag, and stagger behavior.
Co-authored-by: Cursor <cursoragent@cursor.com>
