Limit and label task hierarchy

tests/state.test.ts

@@ -415,7 +415,7 @@ test("enforces per-mutation and per-session task limits atomically", () => {
   );
 });
 
-test("accepts eight task levels and rejects deeper trees atomically", () => {
+test("allows three stored levels beneath the virtual root and rejects deeper task trees atomically", () => {
   const nested = (depth: number) => {
     let task: { name: string; children?: Array<{ name: string; children?: unknown[] }> } = { name: `Level ${depth}` };
     for (let level = depth - 1; level >= 1; level -= 1) {
@@ -425,10 +425,27 @@ test("accepts eight task levels and rejects deeper trees atomically", () => {
   };
 
   const state = new TaskState();
-  state.add([nested(8) as never]);
-  assert.equal(state.list().length, 8);
+  state.add([nested(3) as never, { name: "Other category" }]);
+  assert.equal(state.list().length, 4);
   const before = state.snapshot();
-  assert.throws(() => state.add([nested(9) as never]), /depth must not exceed 8 levels/);
+  assert.throws(() => state.add([nested(4) as never]), /depth must not exceed 3 levels/);
+  assert.deepEqual(state.snapshot(), before);
+  assert.throws(() => state.update([{ id: 4, parentId: 3 }]), /depth must not exceed 3 levels/);
+  assert.deepEqual(state.snapshot(), before);
+
+  assert.throws(
+    () =>
+      state.restore({
+        tasks: [
+          { id: 1, name: "Category", status: "pending", parentId: null, childrenIds: [2] },
+          { id: 2, name: "Item", status: "pending", parentId: 1, childrenIds: [3] },
+          { id: 3, name: "Leaf", status: "pending", parentId: 2, childrenIds: [4] },
+          { id: 4, name: "Too deep", status: "pending", parentId: 3, childrenIds: [] },
+        ],
+        nextId: 5,
+      }),
+    /depth must not exceed 3 levels/,
+  );
   assert.deepEqual(state.snapshot(), before);
 });