Productionize SQLite config with WAL mode and tuned PRAGMAs
Set journal_mode=WAL, busy_timeout, synchronous=NORMAL, foreign_keys,
cache_size, and temp_store on every new connection via Knex pool hook.
This eliminates reader/writer contention across the three processes
(web, jetstream, queue) sharing the same SQLite file.
Also remove stale design context section from AGENTS.md.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>