update.sh now backs up data/corpus_watermark.txt and data/incident_watermark.txt
before git pull and restores them after, mirroring the existing watch.yaml pattern.
Without this, an update would reset watermarks to zero and re-push all corpus
entries from the beginning on the next export run.
.env.example adds a corpus export section documenting the three env vars
needed to opt a node into the Avocet training pipeline.
Closes: #6
update.sh pulls a named branch (default: main), preserves the local
watch.yaml around the pull, rebuilds the image, restarts the service,
and polls health until ready.
Usage: sudo bash /opt/turnstone/scripts/update.sh [branch]
patterns/watch.yaml is site-specific config — gitignored so host
customizations survive git pulls. The template is preserved in git
history (feat/live-watch) for reference.
