Persistence test matrix

• first run with blank/invalid storage;

• valid current version;

• out-of-range field;

• unknown old/new version;

• save, script reload, slot reload, and power cycle;

• maximum/minimum and signed values;

• field at a storage boundary;

• maximum record/index;

• reset to immutable defaults;

• cancelled edit does not save;

• explicit save commits exactly once.