The previous guard compared the pinned design against the live
activeDesignId (the selection). On a design switch the selection flips
synchronously while the new canvas loads asynchronously, so the
on-screen nodes briefly still belong to the previous design — arming the
timer with the newly-selected id would save those stale nodes under the
wrong design. Track the design the canvas was actually loaded as
(loadedDesignId provenance) and gate autosave on that instead: pin it
when the timer is armed and re-check the live provenance at fire time,
skipping the save if a different canvas has since loaded.
Also validate the persisted `enabled` flag by type (mirror of `delay`),
and add the matching regression tests (provenance switch skip, enabled
type validation).
ha-relevant: maybe