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/client/usage.test.ts

@@ -1,10 +1,10 @@
 /**
- * # Using the quack Client
+ * # Using the quak Client
  *
  * This test file is a tutorial. It walks through every operation the
  * library supports, in the order you would use them in a real program.
  * Each `it()` block is a self-contained example with commentary
- * explaining what is happening and why. If you are reading the quack
+ * explaining what is happening and why. If you are reading the quak
  * source for the first time, start here.
  *
  * The tests run against a mock Ente server built from the same SRP and
@@ -30,7 +30,7 @@
  * All you need is the `Client` class:
  *
  * ```ts
- * import { Client } from "quack";
+ * import { Client } from "quak";
  * ```
  *
  * The Client wraps every lower-level module (crypto, auth, api, model,
@@ -332,7 +332,7 @@ beforeAll(async () => {
     await init();
     await sodium.ready;
     server = await buildServer();
-    testDir = mkdtempSync(join(tmpdir(), "quack-usage-test-"));
+    testDir = mkdtempSync(join(tmpdir(), "quak-usage-test-"));
 });
 
 afterAll(() => {
@@ -344,7 +344,7 @@ afterAll(() => {
 // The tutorial
 // ---------------------------------------------------------------------------
 
-describe("quack Client usage guide", () => {
+describe("quak Client usage guide", () => {
     /**
      * ## 1. Logging in
      *