json_to_ipld handled $link (→ Ipld::Link) but treated $bytes objects as regular maps, producing a CBOR map (major type 5) instead of a byte string (major type 2). This caused downstream consumers expecting spec-compliant CBOR — notably Jetstream's atdata.UnmarshalCBOR — to fail with "decoding $byte value: illegal base64 data". Decode $bytes from standard base64 (RFC 4648 §4, padding optional) into Ipld::Bytes, matching the existing $link handling pattern.