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/plugins/page-seo.test.ts

@@ -0,0 +1,85 @@
+import { describe, expect, it } from "vitest";
+
+import { buildBlogPostingJsonLd } from "../../../src/page/jsonld.js";
+import { generateBaseSeoContributions } from "../../../src/page/seo-contributions.js";
+import type { PublicPageContext } from "../../../src/plugins/types.js";
+
+function createPage(overrides: Partial<PublicPageContext> = {}): PublicPageContext {
+	return {
+		url: "https://example.com/posts/hello",
+		path: "/posts/hello",
+		locale: null,
+		kind: "content",
+		pageType: "article",
+		title: "Hello World | My Site",
+		description: "Test description",
+		canonical: "https://example.com/posts/hello",
+		image: "https://example.com/og.png",
+		siteName: "My Site",
+		...overrides,
+	};
+}
+
+describe("page SEO metadata", () => {
+	it("uses pageTitle for og:title and twitter:title", () => {
+		const page = createPage({ pageTitle: "Hello World" });
+
+		const contributions = generateBaseSeoContributions(page);
+
+		expect(contributions).toContainEqual({
+			kind: "property",
+			property: "og:title",
+			content: "Hello World",
+		});
+		expect(contributions).toContainEqual({
+			kind: "meta",
+			name: "twitter:title",
+			content: "Hello World",
+		});
+	});
+
+	it("prefers explicit seo.ogTitle over pageTitle", () => {
+		const page = createPage({
+			seo: { ogTitle: "Custom OG Title" },
+			pageTitle: "Hello World",
+		});
+
+		const contributions = generateBaseSeoContributions(page);
+
+		expect(contributions).toContainEqual({
+			kind: "property",
+			property: "og:title",
+			content: "Custom OG Title",
+		});
+		expect(contributions).toContainEqual({
+			kind: "meta",
+			name: "twitter:title",
+			content: "Custom OG Title",
+		});
+	});
+
+	it("falls back to title when pageTitle is absent", () => {
+		const page = createPage();
+
+		const contributions = generateBaseSeoContributions(page);
+
+		expect(contributions).toContainEqual({
+			kind: "property",
+			property: "og:title",
+			content: "Hello World | My Site",
+		});
+	});
+
+	it("uses pageTitle for article JSON-LD headline", () => {
+		const page = createPage({
+			articleMeta: { publishedTime: "2026-04-03T12:00:00.000Z" },
+			pageTitle: "Hello World",
+		});
+
+		const graph = buildBlogPostingJsonLd(page);
+
+		expect(graph).toMatchObject({
+			headline: "Hello World",
+		});
+	});
+});