fix(font-atlas): the atlas destroys its image

FontAtlas::Initialize creates an ImageVulkan and nothing ever called its
Destroy(): every atlas left its 1024x1024 image, memory and view behind.
The atlas now owns the image for its lifetime and is no longer copyable.
ImageVulkan's handles start as VK_NULL_HANDLE and Destroy() resets them,
so an atlas that was never initialised, or an image destroyed by hand
before the atlas goes, is a no-op in the destructor.

The owner waits for the GPU before the atlas goes and, in sets mode,
destroys the descriptor heap that holds the image's view before the atlas.

interfaces/Crafter.Graphics-FontAtlas.cppm

@@ -96,6 +96,18 @@ export namespace Crafter {
         bool dirty = false;
         DirtyRect dirtyRect;
 
+#ifndef CRAFTER_GRAPHICS_WINDOW_DOM
+        FontAtlas() = default;
+        FontAtlas(const FontAtlas&) = delete;
+        FontAtlas& operator=(const FontAtlas&) = delete;
+        // The image goes with the atlas. The owner waits for the GPU first
+        // and, in sets mode, destroys the heap holding the image's view before
+        // the atlas.
+        ~FontAtlas() {
+            if (image.image != VK_NULL_HANDLE) image.Destroy();
+        }
+#endif
+
         void Initialize(GraphicsCommandBuffer cmd);
 
         // Returns the row-major byte pointer the CPU writes pixels into.