Remove the orphaned post-session dust accumulator from gardener-agent.sh
(no longer reached after #367 moved gardener-poll.sh to action issues).
Add a dedicated dust-bundling formula step to run-gardener.toml that
handles the full lifecycle: dedup, timestamps, 30-day TTL expiry, and
bundling groups with 3+ items into backlog issues.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
