feat(docs): clarify direct minting memo formats with prefix details

Author: fassko

docs/fassets/03-direct-minting.mdx

@@ -45,7 +45,9 @@ There are two supported formats:
 
 **32-byte memo** (recipient only):
 
-A standard direct minting payment reference that encodes only the 20-byte recipient address.
+1. **8-byte prefix**: `0x4642505266410018` (`DIRECT_MINTING`)
+2. **20-byte recipient address**
+
 Anyone can execute, as no executor is specified.
 
 **48-byte memo** (recipient and executor):