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/after.test.ts

@@ -0,0 +1,56 @@
+import { describe, expect, it, vi } from "vitest";
+
+// Default stub: no host-provided waitUntil. Mirrors what Node (and
+// any adapter that doesn't implement the virtual) sees at runtime.
+vi.mock("virtual:emdash/wait-until", () => ({ waitUntil: undefined }), { virtual: true });
+
+// The waitUntil-handoff path is exercised end-to-end by the cron
+// integration in emdash-runtime.ts; testing it here would require
+// swapping out a module that's already bound at load time, which
+// fights vitest's module cache. These unit tests cover the three
+// behaviors that don't need a real waitUntil: the callback fires,
+// errors don't escape, and the caller doesn't block.
+import { after } from "../../src/after.js";
+
+describe("after()", () => {
+	it("runs the callback", async () => {
+		const fn = vi.fn();
+		after(fn);
+		await new Promise((r) => setTimeout(r, 0));
+		expect(fn).toHaveBeenCalledTimes(1);
+	});
+
+	it("swallows errors and logs them with the emdash prefix", async () => {
+		const errorSpy = vi.spyOn(console, "error").mockImplementation(() => {});
+		const boom = new Error("boom");
+
+		try {
+			expect(() =>
+				after(async () => {
+					throw boom;
+				}),
+			).not.toThrow();
+
+			await new Promise((r) => setTimeout(r, 0));
+
+			expect(errorSpy).toHaveBeenCalledWith(
+				expect.stringContaining("[emdash] deferred task failed"),
+				boom,
+			);
+		} finally {
+			// Restore unconditionally so a failed assertion above doesn't leak
+			// the spy into later tests.
+			errorSpy.mockRestore();
+		}
+	});
+
+	it("returns synchronously without waiting for the callback", async () => {
+		let ran = false;
+		after(async () => {
+			await new Promise((r) => setTimeout(r, 10));
+			ran = true;
+		});
+		// after() returned already — the callback hasn't completed.
+		expect(ran).toBe(false);
+	});
+});