feat(store): _saveDisabled latch and stronger corruption-wipe coverage

tests/store.test.js

@@ -48,4 +48,25 @@ test('Store: corrupted JSON is wiped with a warning', () => {
   const s = new Store({ storage, onWarn: (m) => warnings.push(m) });
   assert.equal(s.getTarget('strength'), null);
   assert.equal(warnings.length, 1);
+  assert.equal(storage.getItem('tat.targets'), null);
+  const warningsBefore = warnings.length;
+  new Store({ storage, onWarn: (m) => warnings.push(m) });
+  assert.equal(warnings.length, warningsBefore);
+});
+
+test('Store: latches off further saves after a storage write failure', () => {
+  const data = new Map();
+  const throwingStorage = {
+    getItem(k) { return data.has(k) ? data.get(k) : null; },
+    setItem() { throw new Error('quota exceeded'); },
+    removeItem(k) { data.delete(k); },
+    clear() { data.clear(); },
+  };
+  const warnings = [];
+  const s = new Store({ storage: throwingStorage, onWarn: (m) => warnings.push(m) });
+  assert.equal(s.setTarget('strength', 25_000_000), false);
+  assert.equal(s.setTarget('speed', 50_000_000), false);
+  assert.equal(warnings.length, 1);
+  assert.equal(s.getTarget('strength'), 25_000_000);
+  assert.equal(s.getTarget('speed'), 50_000_000);
 });