CaptureRecoveryUnit now builds content in memory and skips writes when the unit
is already current (checksum + dump-set + version), so it can run from RefreshCache
(startup + every 5m) without thrashing the USB drive. Units now exist shortly after
startup and track config changes without waiting for the daily DB dump. +idempotency test.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>