The async engine is created without a busy timeout, so concurrent
writes (agent responses, metrics, session updates) fail instantly
with 'database is locked' instead of waiting for the lock.
Add connect_args={'timeout': 30} for SQLite engines so the driver
waits up to 30 seconds for the write lock. Combined with the existing
WAL journal mode, this handles the typical concurrent write bursts
from agent + metrics + session operations.
Fixes#6443
Yufeng He
acbc5150cf