Clarify process id field ($graph only)

Author: kinow

Process.yml

@@ -455,7 +455,11 @@ $graph:
     - name: id
       type: string?
       jsonldPredicate: "@id"
-      doc: "The unique identifier for this object."
+      doc: |
+        The unique identifier for this object.
+
+        Only useful for `$graph` at `Process` level. Should not be exposed
+        to users in graphical or terminal user interfaces.
 
 
 - name: LoadListingEnum