Этап 2

Minint.Core/Models/MinintContainer.cs

@@ -0,0 +1,35 @@
+namespace Minint.Core.Models;
+
+/// <summary>
+/// Top-level container: holds dimensions shared by all documents/layers,
+/// and a list of documents (frames).
+/// </summary>
+public sealed class MinintContainer
+{
+    public int Width { get; set; }
+    public int Height { get; set; }
+    public List<MinintDocument> Documents { get; }
+
+    public int PixelCount => Width * Height;
+
+    public MinintContainer(int width, int height)
+    {
+        ArgumentOutOfRangeException.ThrowIfLessThan(width, 1);
+        ArgumentOutOfRangeException.ThrowIfLessThan(height, 1);
+
+        Width = width;
+        Height = height;
+        Documents = [];
+    }
+
+    /// <summary>
+    /// Creates a new document with a single transparent layer and adds it to the container.
+    /// </summary>
+    public MinintDocument AddNewDocument(string name)
+    {
+        var doc = new MinintDocument(name);
+        doc.Layers.Add(new MinintLayer("Layer 1", PixelCount));
+        Documents.Add(doc);
+        return doc;
+    }
+}