Validate byte-preserving record fields as base64 strings

docs/integrations/publication-records.md

@@ -42,7 +42,9 @@ endpoint bytes uses version 2 with the same `evidence` object and an additional
 `evidence_bytes` object. Each entry in `evidence_bytes` uses an evidence field
 name and a standard base64 string containing its exact bytes. That entry
 supplies the field's value when loading; the writer omits its lossy string form
-from `evidence`. Unknown field names are ignored. This representation applies
+from `evidence`. Invalid known-field types or base64 encodings produce a
+record-format error with the available decoding cause. Unknown field names are
+ignored. This representation applies
 to every evidence field and preserves the same identity as typed Go evidence.
 Older CLIs that support only version 1 report an unsupported version for these
 byte-containing records; use a CLI supporting version 2 to load them.