lab: take the forge's owner as a required config value, and name no node in its fixtures (issue 1838)

The lab cloned and installed from the owner this mesh's repositories are under, written in its code; another
mesh's forge holds them under its own (1838/AC4). Unset, lab_check, lab_run and a rebuild say so. Fixtures
name neutral machines and an example owner.

modules/lab/module.json

@@ -37,6 +37,12 @@
         "description": "The forge the lab's machines take their packages from, as its address: the operator's, with no default (novox/hq ADR 0112).",
         "trusted": true,
         "required": true
+      },
+      "forge-owner": {
+        "type": "string",
+        "description": "The owner on the forge the mesh's repositories and npm packages are under, such as the organisation that holds them: the operator's, with no default (novox/hq ADR 0507 §9).",
+        "trusted": true,
+        "required": true
       }
     },
   "resources": [