Fix screenshot services using wrong viewport dimensions when designerWidth/Height ≠ 100%

[Copilot]

Both DisplayMediaPngWriterService and ElectronPngWriterService computed tile dimensions from designerCanvas.canvas.offsetWidth/Height, but captured from outercanvas2. When designerWidth is e.g. 200%, the inner canvas is 2× the capture viewport, so each tile covers only half the expected area—producing a screenshot of half the element with a 1px border artifact.

• Use outercanvas2.offsetWidth/Height for viewport dimensions, matching the element actually used for capture

-            const viewportW = designerCanvas.canvas.offsetWidth;
-            const viewportH = designerCanvas.canvas.offsetHeight;
+            const viewportElement = (<DesignerCanvas>designerCanvas).outercanvas2;
+            const viewportW = viewportElement.offsetWidth;
+            const viewportH = viewportElement.offsetHeight;

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.