Tests for the entire crypto/ public surface, written against the API
shape declared in the README. The accompanying src/crypto/ modules are
stubs that throw 'not implemented' so the test files compile and tests
fail with clear errors rather than module-not-found.
Tests cover:
* init() resolves and is idempotent
* fromBase64 / toBase64 / toBase64URL round-trips, including URL-safe
input with stripped padding (the form Ente uses for auth tokens)
* deriveKEK matches sodium.crypto_pwhash with Argon2id parameters
* deriveLoginSubkey matches sodium.crypto_kdf_derive_from_key with
subkey id 1 and ctx 'loginctx', truncated to 16 bytes
* decryptBox round-trips, rejects tampering, wrong key, wrong nonce
* decryptSealed round-trips, rejects wrong keypair and tampering
* Secretstream pull decrypts multi-chunk streams in order, exposes
per-chunk tags, rejects tampering, wrong key, and out-of-order chunks
* Constants STREAM_CHUNK_SIZE (4 MiB) and STREAM_CHUNK_OVERHEAD (17)
Tests are commented to serve as the canonical API documentation per the
README development workflow policy. Verified: 29 tests fail (red), 3
trivial constant tests pass; lint and fmt-check are green.
eslint.config.mjs is updated to honour the leading-underscore convention
for intentionally unused parameters (the stubs).
package.json declares the project as ESM with NodeNext module resolution,
exposing dist/index.js as the library entry and dist/bin/quack.js as the
CLI binary. Dev dependencies are pinned to exact versions (yarn.lock holds
the integrity hashes per repo policy on hash-pinned external references).
Adds a placeholder src/index.ts and a single smoke test so make check is
not a no-op.
