server-v0.0.8

Emergency patch for stores upgraded from a 0.0.7 release candidate.

- **Upgrading an rc store to 0.0.7 silently wiped search vectors** (#1524): the migration adoption step pruned the pgvector embedding columns, so pre-existing documents stayed listed but returned no search results while new documents worked. The adoption heal no longer touches columns.
- **Automatic repair**: on boot, 0.0.8 detects rows whose vectors are missing while their text survives and re-embeds them in the background — stores already damaged by the 0.0.7 upgrade heal themselves on the first start, no manual steps.
- The migration test matrix now seeds real vectors into its legacy-store fixtures and asserts they survive upgrades.

If you upgraded from 0.0.7-rc.x to 0.0.7 and lost search results: install 0.0.8 and start the server — you should see `[vector-backfill] Restored search vectors …` once it finishes.