feat(lib): shelf sort/section pure helpers + formatSize extraction, table tests

frontend/test/format.test.ts

@@ -0,0 +1,18 @@
+import { describe, expect, it } from "vitest";
+import { formatSize } from "../src/lib/format";
+
+describe("formatSize", () => {
+  it("renders human sizes across units", () => {
+    expect(formatSize(0)).toBe("");
+    expect(formatSize(512)).toBe("512 B");
+    expect(formatSize(2048)).toBe("2.0 KB");
+    expect(formatSize(15 * 1024 * 1024)).toBe("15 MB");
+    expect(formatSize(3.2 * 1024 ** 3)).toBe("3.2 GB");
+  });
+
+  it("returns empty for non-positive and keeps one decimal below 10", () => {
+    expect(formatSize(-1)).toBe("");
+    expect(formatSize(1024)).toBe("1.0 KB");
+    expect(formatSize(10 * 1024)).toBe("10 KB");
+  });
+});