docs(workflow-workspace): mirror the backend output in the block catalog (AIW-287)

Author: outof-place

docs/workflow-workspace/index.html

@@ -1220,6 +1220,7 @@ <h1>Workflow Design Workspace</h1>
           optionalOutputs: [
             ...typedPaths("unknown[]", "findings"),
             ...typedPaths("string", "reason"),
+            ...typedPaths("string", "backend"),
           ],
           statuses: ["ok", "flagged", "skipped"],
         }),