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/utils/chunks.test.ts

@@ -0,0 +1,38 @@
+import { describe, expect, it } from "vitest";
+
+import { chunks, SQL_BATCH_SIZE } from "../../../src/utils/chunks.js";
+
+describe("chunks", () => {
+	it("returns empty array for empty input", () => {
+		expect(chunks([], 10)).toEqual([]);
+	});
+
+	it("returns single chunk when array fits within size", () => {
+		expect(chunks([1, 2, 3], 5)).toEqual([[1, 2, 3]]);
+	});
+
+	it("splits array into even chunks", () => {
+		expect(chunks([1, 2, 3, 4], 2)).toEqual([
+			[1, 2],
+			[3, 4],
+		]);
+	});
+
+	it("handles remainder in last chunk", () => {
+		expect(chunks([1, 2, 3, 4, 5], 2)).toEqual([[1, 2], [3, 4], [5]]);
+	});
+
+	it("handles chunk size of 1", () => {
+		expect(chunks([1, 2, 3], 1)).toEqual([[1], [2], [3]]);
+	});
+
+	it("handles array exactly equal to chunk size", () => {
+		expect(chunks([1, 2, 3], 3)).toEqual([[1, 2, 3]]);
+	});
+});
+
+describe("SQL_BATCH_SIZE", () => {
+	it("is 50", () => {
+		expect(SQL_BATCH_SIZE).toBe(50);
+	});
+});