Pref was calculated as table_number × 10, meaning moving a .list between
groups didn't change its priority. Now pref is assigned sequentially by
group/list processing order (base=1000, group_step=100, list_step=10).

Also improves cleanup_state to detect .list files moved between groups —
only removes old state dir without flushing the shared routing table.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>