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/integration/fixture/.emdash/seed.json

@@ -0,0 +1,94 @@
+{
+	"$schema": "https://emdashcms.com/seed.schema.json",
+	"version": "1",
+	"meta": {
+		"name": "E2E Test Fixture",
+		"description": "Schema for E2E tests"
+	},
+	"taxonomies": [
+		{
+			"name": "categories",
+			"label": "Categories",
+			"labelSingular": "Category",
+			"hierarchical": true,
+			"collections": ["posts"],
+			"terms": [
+				{ "slug": "news", "label": "News" },
+				{ "slug": "tutorials", "label": "Tutorials" },
+				{ "slug": "opinion", "label": "Opinion" }
+			]
+		}
+	],
+	"sections": [
+		{
+			"slug": "hero",
+			"title": "Hero Section",
+			"description": "Main hero area",
+			"content": [
+				{
+					"_type": "block",
+					"_key": "b1",
+					"style": "normal",
+					"children": [{ "_type": "span", "_key": "s1", "text": "Welcome to our site" }],
+					"markDefs": []
+				}
+			]
+		}
+	],
+	"collections": [
+		{
+			"slug": "posts",
+			"label": "Posts",
+			"labelSingular": "Post",
+			"fields": [
+				{
+					"slug": "title",
+					"label": "Title",
+					"type": "string",
+					"required": true
+				},
+				{
+					"slug": "body",
+					"label": "Body",
+					"type": "portableText"
+				},
+				{
+					"slug": "excerpt",
+					"label": "Excerpt",
+					"type": "text"
+				},
+				{
+					"slug": "theme_color",
+					"label": "Theme Color",
+					"type": "string",
+					"widget": "color:picker"
+				}
+			]
+		},
+		{
+			"slug": "pages",
+			"label": "Pages",
+			"labelSingular": "Page",
+			"fields": [
+				{
+					"slug": "title",
+					"label": "Title",
+					"type": "string",
+					"required": true
+				},
+				{
+					"slug": "body",
+					"label": "Body",
+					"type": "portableText"
+				}
+			]
+		}
+	],
+	"bylines": [
+		{
+			"id": "fixture-editorial",
+			"slug": "fixture-editorial",
+			"displayName": "Fixture Editorial"
+		}
+	]
+}