Use contextual descriptors for entity reconciliation

assets/dnd/entity-reconciliation/schemas/dnd_entity_reconcile_llm.v1.json

@@ -14,9 +14,32 @@
         "properties": {
           "members": {
             "type": "array",
-            "items": {"type": "string"}
+            "items": {"$ref": "#/$defs/selector"}
           },
-          "canonical": {"type": "string"}
+          "canonical": {"$ref": "#/$defs/selector"}
+        }
+      }
+    }
+  },
+  "$defs": {
+    "selector": {
+      "type": "object",
+      "additionalProperties": false,
+      "required": ["name", "source_refs"],
+      "properties": {
+        "name": {"type": "string", "minLength": 1},
+        "source_refs": {
+          "type": "array",
+          "minItems": 1,
+          "items": {
+            "type": "object",
+            "additionalProperties": false,
+            "required": ["start_unit_id", "end_unit_id"],
+            "properties": {
+              "start_unit_id": {"type": "integer", "minimum": 1},
+              "end_unit_id": {"type": "integer", "minimum": 1}
+            }
+          }
         }
       }
     }