Fix Task.tasks field type: rename Children []*Task to ChildIDs []int

The Checkvist API returns the 'tasks' field as an array of child task IDs
(integers), not as full Task objects. This was causing JSON unmarshal errors.

BREAKING CHANGE: Task.Children []*Task renamed to Task.ChildIDs []int

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- **BREAKING**: `Task.Children []*Task` renamed to `Task.ChildIDs []int` to match API response format (API returns array of child task IDs, not full task objects)
+
 ### Fixed
 
 - **Tasks**: Fix `Close()`, `Reopen()`, and `Invalidate()` to handle API array response format

models.go

@@ -140,8 +140,8 @@ type Task struct {
 	UpdatedAt APITime `json:"updated_at"`
 	// CreatedAt is the timestamp when the task was created.
 	CreatedAt APITime `json:"created_at"`
-	// Children contains nested child tasks (when fetched with tree structure).
-	Children []*Task `json:"tasks,omitempty"`
+	// ChildIDs contains IDs of child tasks (returned by API as array of integers).
+	ChildIDs []int `json:"tasks,omitempty"`
 	// Notes contains the comments/notes attached to this task.
 	Notes []Note `json:"notes,omitempty"`
 }

tasks_test.go

@@ -73,6 +73,60 @@ func TestTasks_Get(t *testing.T) {
 	}
 }
 
+func TestTask_ChildIDs_Unmarshal(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+
+		switch r.URL.Path {
+		case "/auth/login.json":
+			json.NewEncoder(w).Encode(map[string]string{"token": "test-token"})
+		case "/checklists/1/tasks/101.json":
+			w.Write(loadFixture(t, "testdata/tasks/single.json"))
+		case "/checklists/1/tasks.json":
+			w.Write(loadFixture(t, "testdata/tasks/list.json"))
+		default:
+			t.Errorf("unexpected path: %s", r.URL.Path)
+		}
+	}))
+	defer server.Close()
+
+	client := NewClient("user@example.com", "api-key", WithBaseURL(server.URL))
+
+	t.Run("single task with child IDs", func(t *testing.T) {
+		task, err := client.Tasks(1).Get(context.Background(), 101)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		expectedChildIDs := []int{201, 202, 203}
+		if len(task.ChildIDs) != len(expectedChildIDs) {
+			t.Fatalf("expected %d child IDs, got %d", len(expectedChildIDs), len(task.ChildIDs))
+		}
+		for i, id := range expectedChildIDs {
+			if task.ChildIDs[i] != id {
+				t.Errorf("expected ChildIDs[%d] = %d, got %d", i, id, task.ChildIDs[i])
+			}
+		}
+	})
+
+	t.Run("list with mixed child IDs", func(t *testing.T) {
+		tasks, err := client.Tasks(1).List(context.Background())
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		// First task has child IDs [201, 202]
+		if len(tasks[0].ChildIDs) != 2 {
+			t.Errorf("expected 2 child IDs for first task, got %d", len(tasks[0].ChildIDs))
+		}
+		if tasks[0].ChildIDs[0] != 201 || tasks[0].ChildIDs[1] != 202 {
+			t.Errorf("expected ChildIDs [201, 202], got %v", tasks[0].ChildIDs)
+		}
+		// Second task has empty child IDs
+		if len(tasks[1].ChildIDs) != 0 {
+			t.Errorf("expected 0 child IDs for second task, got %d", len(tasks[1].ChildIDs))
+		}
+	})
+}
+
 func TestTasks_Create(t *testing.T) {
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")

testdata/tasks/list.json

@@ -13,7 +13,8 @@
     "comments_count": 0,
     "update_line": "",
     "updated_at": "2026/01/14 10:00:00 +0000",
-    "created_at": "2026/01/10 09:00:00 +0000"
+    "created_at": "2026/01/10 09:00:00 +0000",
+    "tasks": [201, 202]
   },
   {
     "id": 102,
@@ -29,6 +30,7 @@
     "comments_count": 3,
     "update_line": "",
     "updated_at": "2026/01/14 11:00:00 +0000",
-    "created_at": "2026/01/11 10:00:00 +0000"
+    "created_at": "2026/01/11 10:00:00 +0000",
+    "tasks": []
   }
 ]

testdata/tasks/single.json

@@ -12,5 +12,6 @@
   "comments_count": 0,
   "update_line": "",
   "updated_at": "2026/01/14 10:00:00 +0000",
-  "created_at": "2026/01/10 09:00:00 +0000"
+  "created_at": "2026/01/10 09:00:00 +0000",
+  "tasks": [201, 202, 203]
 }