Close the disk-fill trap: with wal_autocheckpoint=0 a dead worker means nothing checkpoints.
Controller now respawns an unexpectedly-dead worker (bounded: RespawnMax/RespawnWindowMs +
backoff); on exhaustion it re-arms a conservative inline autocheckpoint (FallbackPages) on the
main connection + reclaims the backlog, logging loudly. Clean stopWalCheckpointer() teardown is
distinguished via a 'stopping' flag so SIGTERM never triggers respawn. Env-gated worker
fault-injection (WAL_CKPT_FAIL_START) for tests. Local only — no bump/tag.
Disable wal_autocheckpoint on the main connection; run PASSIVE checkpoints from a
worker_threads worker with its OWN better-sqlite3 handle, escalating to TRUNCATE on a
size high-water or PASSIVE-starvation. Removes the synchronous fsync-heavy checkpoint
from the event loop. Config: walCheckpointIntervalMs/HighWaterMB/StarvationRuns.
Local only — no bump/tag.
