Bound external result file reads

docs/integrations/scriptorium.md

@@ -46,6 +46,9 @@ Run behavior:
 - `run` exit code `2` is mapped to `ValidationFailed=true`;
 - successful subprocess still fails if output file is missing or empty.
 
+Each artifact result is limited to 64 MiB and must be a regular file without
+symlinked path components.
+
 Render behavior:
 - subprocess errors propagate;
 - output file must exist and be non-empty.