0.11.0: arc42 and ArchiMate examples; ref in every diagram kind

Six example models next to the three C4 ones: arc42 (Cinema Tickets, IoT
Telemetry, Team Wiki) by section, ArchiMate (Insurance Claims, HR
Onboarding, Logistics Tracking) by layer, each validated with 0 errors and
0 warnings. resolveRefs and the editor schemas now take ref: in workflow
and dataflow nodes, sequence participants and lifecycle states, as the
skill already did. Example tests check each framework's folders.

schemas/sequence.schema.json

@@ -117,11 +117,6 @@
       "items": {
         "type": "object",
         "additionalProperties": false,
-        "required": [
-          "id",
-          "type",
-          "label"
-        ],
         "properties": {
           "id": {
             "$ref": "common.schema.json#/$defs/id"
@@ -152,8 +147,31 @@
               "minLength": 1
             },
             "description": "Ids of architecture decisions (*.archify-decision files of the model) this is about. Shown in the Decisions panel under the diagram."
+          },
+          "ref": {
+            "type": "string",
+            "pattern": "^[a-zA-Z][a-zA-Z0-9_-]*$",
+            "description": "A shared element from the model’s registry (*.archify-registry). Its type, label, sublabel, brand and sources come from there; the diagram adds its own placement and may override label, sublabel and tag."
+          },
+          "diagram": {
+            "type": "string",
+            "description": "Diagram that explains this element, relative to the model root (main.archify). Double-click the node to open it."
           }
-        }
+        },
+        "anyOf": [
+          {
+            "required": [
+              "ref"
+            ]
+          },
+          {
+            "required": [
+              "id",
+              "type",
+              "label"
+            ]
+          }
+        ]
       }
     },
     "segments": {