Persistence diagnosis

Trace/check:

• magic and schema version;

• load result after range validation;

• runtime copy after editing;

• dirty flag;

• save event;

• computed SPVAR/BVAR index;

• value after script reload and power cycle.

Common causes are mismatched save/load order, changed bit width, missing version bump, wrong identity key, out-of-range default substitution, and saving a stale cache.