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/crypto/box.test.ts

@@ -1,7 +1,7 @@
 /**
  * Tests for `crypto.decryptBox` and `crypto.decryptSealed`.
  *
- * These cover the two asymmetric-and-symmetric "box" primitives quack uses
+ * These cover the two asymmetric-and-symmetric "box" primitives quak uses
  * to unwrap key material from Ente:
  *
  *   - `decryptBox`: secretbox decryption. Used everywhere a small payload
@@ -18,7 +18,7 @@
  *
  *       authToken = decryptSealed(encryptedToken, publicKey, secretKey)
  *
- * Encryption is server-side; quack only ever decrypts.
+ * Encryption is server-side; quak only ever decrypts.
  */
 
 import sodium from "libsodium-wrappers-sumo";