Rename quack to quak

German for 'quack', matching the Ente (German for 'duck') naming. All
references updated: package name, CLI binary, X-Client-Package header,
test descriptions, temp dir prefixes, README, Makefile docker tag.

test/smoke.test.ts

@@ -1,7 +1,7 @@
 import { describe, expect, it } from "vitest";
 import { VERSION } from "../src/index.js";
 
-describe("quack", () => {
+describe("quak", () => {
     it("exports a version string", () => {
         expect(typeof VERSION).toBe("string");
         expect(VERSION.length).toBeGreaterThan(0);