Capability: crypto-noble-defaults

ADDED Requirements

REQ-NOBLE-010: Exports aeadEncrypt(algo: AeadAlgorithm, key: Uint8Array, plaintext: Uint8Array, options: AeadEncryptOptions, opts?: { engine?: AeadEngine }): Uint8Array.
REQ-NOBLE-011: Exports aeadDecrypt(algo: AeadAlgorithm, key: Uint8Array, ciphertext: Uint8Array, options: AeadDecryptOptions, opts?: { engine?: AeadEngine }): Uint8Array.
REQ-NOBLE-012: AeadEncryptOptions = { nonce: Uint8Array; aad?: Uint8Array }. AeadDecryptOptions is the same shape.
REQ-NOBLE-013: Default engine is noble: @noble/ciphers AES-256-GCM and ChaCha20-Poly1305; @noble/ciphers XChaCha20-Poly1305.
REQ-NOBLE-014: Key must be 32 bytes; throws CryptoError("CRYPTO.KEY.INVALID_LENGTH") otherwise.
REQ-NOBLE-015: Nonce must be 12 bytes for AES-256-GCM and ChaCha20-Poly1305, 24 bytes for XChaCha20-Poly1305; throws CryptoError("CRYPTO.AEAD.INVALID_NONCE") otherwise.
REQ-NOBLE-016: Exports AEAD_KEY_LENGTH = 32, AEAD_NONCE_LENGTH = 12, AEAD_XCHACHA_NONCE_LENGTH = 24.

REQ-NOBLE-020: Exports ed25519 namespace: { generateKeypair(opts?), sign(secretKey, message), verify(publicKey, signature, message) }.
REQ-NOBLE-021: Exports ecdsaP256 namespace: same shape as ed25519.
REQ-NOBLE-022: All functions accept { engine?: SignEngine } as a trailing options arg.
REQ-NOBLE-023: Noble defaults: @noble/curves ed25519 and P-256.
REQ-NOBLE-024: verify always returns boolean, never throws on a bad signature.
REQ-NOBLE-025: ecdsaP256.generateKeypair retries until noble.utils.isValidSecretKey(secretKey) is true.

REQ-NOBLE-030: Exports x25519 namespace: { generateKeypair(opts?), agree(mySecret, theirPublic) }.
REQ-NOBLE-031: Accepts { engine?: AgreeEngine }.
REQ-NOBLE-032: Noble default: @noble/curves x25519.

REQ-NOBLE-040: Exports sealedBox namespace: { seal(recipientPublic, plaintext, opts?), open(recipientSecret, recipientPublic, ciphertext, opts?) }.
REQ-NOBLE-041: Noble default: X25519 key agreement + XChaCha20-Poly1305 encryption (crypto_box_seal semantics).

REQ-NOBLE-050: Exports authBox namespace: { seal(senderSecret, recipientPublic, plaintext, nonce, opts?), open(senderPublic, recipientSecret, ciphertext, nonce, opts?) }.
REQ-NOBLE-051: Noble default: X25519 key agreement + XChaCha20-Poly1305 (crypto_box semantics).

REQ-NOBLE-060: Exports ED25519_SECRET_KEY_LENGTH = 32, ED25519_PUBLIC_KEY_LENGTH = 32, ED25519_SIGNATURE_LENGTH = 64, X25519_KEY_LENGTH = 32, ECDSA_P256_SIGNATURE_LENGTH = 64.