Collections shared with the account are not encrypted with the master
key: the sharer only knows the recipient's public key, so the server
delivers encryptedKey as crypto_box_seal to that key and omits
keyDecryptionNonce entirely. decryptCollection assumed the owned-only
wire format and crashed on fromBase64(undefined) for any account with
an incoming shared album, taking down listCollections and every
command built on it (backup, backup-metadata, ...).
The previous "shared" fixture was unfaithful (secretbox + nonce with a
foreign ownerID, a shape the server never sends), which is why the
suite stayed green. These tests model the real wire format and change
decryptCollection to take the full key material {masterKey, publicKey,
secretKey} so it can unseal shared collection keys.
sneak
59e0aa7d47