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/vitest.config.ts

@@ -0,0 +1,61 @@
+import { defineConfig } from "vitest/config";
+
+// Stub the adapter-provided virtual modules that runtime code imports.
+// Individual tests still `vi.mock()` the ones they care about; this plugin
+// just prevents "cannot find package" errors when a test pulls in a chunk
+// of core that happens to touch one transitively. Mirrors the pattern the
+// Astro integration's vite plugin uses at build time.
+const virtualStubs: Record<string, string> = {
+	"virtual:emdash/wait-until": "export const waitUntil = undefined;",
+	// Default-export an empty config so modules that read top-level fields
+	// (e.g. `virtualConfig?.i18n?.defaultLocale`) don't blow up on import.
+	// Tests that need real config still `vi.mock(...)` their own.
+	"virtual:emdash/config": "export default {};",
+};
+
+export default defineConfig({
+	plugins: [
+		{
+			name: "emdash-virtual-stubs",
+			resolveId(id) {
+				// Object.hasOwn — not `in` — so prototype-chain properties
+				// (toString, hasOwnProperty, etc.) aren't accidentally matched.
+				if (Object.hasOwn(virtualStubs, id)) return "\0" + id;
+				return null;
+			},
+			load(id) {
+				if (!id.startsWith("\0virtual:emdash/")) return null;
+				const key = id.slice(1);
+				if (Object.hasOwn(virtualStubs, key)) return virtualStubs[key];
+				return null;
+			},
+		},
+	],
+	test: {
+		globals: true,
+		environment: "node",
+		include: ["tests/**/*.test.ts"],
+		// Server integration tests (cli, client, smoke) start real Astro dev
+		// servers and need a full workspace build — run them in a dedicated
+		// CI job, not via `pnpm test`.
+		// The fixture has symlinked node_modules that contain test files
+		// from transitive deps (zod, emdash) — exclude them too.
+		exclude: [
+			"tests/integration/smoke/**",
+			"tests/integration/cli/**",
+			"tests/integration/client/**",
+			"tests/integration/media/**",
+			"tests/integration/fixture/**",
+		],
+		coverage: {
+			provider: "v8",
+			reporter: ["text", "json", "html"],
+			thresholds: {
+				statements: 80,
+				branches: 80,
+				functions: 80,
+				lines: 80,
+			},
+		},
+	},
+});