Ports the still-unmerged remnant of PR #1891 (#1593 follow-up). Master's
getConfig gained retry-with-reconnect in #1603, but its siblings —
setConfig, unsetConfig, listConfigKeys — still touched `this.sql` bare, so
the first config write/list after a mid-cycle instance-pool teardown threw
the retryable "No database connection" (issue #1678) unhandled instead of
rebuilding the pool.
Adds the connRetry helper from #1891 (same retry+reconnect posture as
batchRetry, but no batch audit JSONL — a config accessor is not a sized
batch), refactors getConfig onto it, and wraps the other three. Writes are
safe to retry: withRetry only retries connection-class failures and both
writes are idempotent (upsert / delete).
Co-authored-by: Sinabina <sinabina@Sinabinas-MacBook-Pro-4.local>
Co-authored-by: jalagrange <jalagrange@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
