Emdash source with visual editor image upload fix

Fixes:
1. media.ts: wrap placeholder generation in try-catch
2. toolbar.ts: check r.ok, display error message in popover

packages/core/tests/unit/converters/image-dimensions.test.ts

@@ -0,0 +1,60 @@
+import { describe, it, expect } from "vitest";
+
+import { portableTextToProsemirror } from "../../../src/content/converters/portable-text-to-prosemirror.js";
+import { prosemirrorToPortableText } from "../../../src/content/converters/prosemirror-to-portable-text.js";
+import type { PortableTextImageBlock } from "../../../src/content/converters/types.js";
+
+describe("Image dimension round-trip", () => {
+	const imageBlock: PortableTextImageBlock = {
+		_type: "image",
+		_key: "abc123",
+		asset: { _ref: "media-123", url: "https://example.com/photo.jpg" },
+		alt: "A photo",
+		caption: "My caption",
+		width: 1920,
+		height: 1080,
+		displayWidth: 400,
+		displayHeight: 225,
+	};
+
+	it("preserves displayWidth and displayHeight through PT → PM → PT", () => {
+		// PT → PM
+		const pm = portableTextToProsemirror([imageBlock]);
+		const imageNode = pm.content[0];
+
+		expect(imageNode.type).toBe("image");
+		expect(imageNode.attrs?.displayWidth).toBe(400);
+		expect(imageNode.attrs?.displayHeight).toBe(225);
+		expect(imageNode.attrs?.width).toBe(1920);
+		expect(imageNode.attrs?.height).toBe(1080);
+
+		// PM → PT
+		const pt = prosemirrorToPortableText(pm);
+		const restored = pt[0] as PortableTextImageBlock;
+
+		expect(restored._type).toBe("image");
+		expect(restored.displayWidth).toBe(400);
+		expect(restored.displayHeight).toBe(225);
+		expect(restored.width).toBe(1920);
+		expect(restored.height).toBe(1080);
+	});
+
+	it("handles images without display dimensions", () => {
+		const noDisplayDims: PortableTextImageBlock = {
+			_type: "image",
+			_key: "def456",
+			asset: { _ref: "media-456", url: "https://example.com/other.jpg" },
+			width: 800,
+			height: 600,
+		};
+
+		const pm = portableTextToProsemirror([noDisplayDims]);
+		const pt = prosemirrorToPortableText(pm);
+		const restored = pt[0] as PortableTextImageBlock;
+
+		expect(restored.displayWidth).toBeUndefined();
+		expect(restored.displayHeight).toBeUndefined();
+		expect(restored.width).toBe(800);
+		expect(restored.height).toBe(600);
+	});
+});