explore: switch to live-tail mode, extend stream window to 55s
Jetstream doesn't replay custom lexicon commits via cursor — only
identity/account events replay. Always live-tail (no cursor param)
and rely on D1 UNIQUE constraints for deduplication. Extended stream
window from 25s to 55s to minimize gaps in the 60s cron cycle.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>