merge: add CreateAdminNPC no-op comparison fixture

hwe/compare/fixtures/monthly_create_admin_npc.json

@@ -0,0 +1,9 @@
+{
+  "action": "CreateAdminNPC",
+  "environment": {
+    "year": 193,
+    "month": 12,
+    "startyear": 190
+  },
+  "observe": {}
+}

hwe/compare/monthly_event_trace.php

@@ -184,6 +184,7 @@ function comparisonMonthlyEventTraceMain(): void
             'UpdateNationLevel',
             'ProcessSemiAnnual',
             'ProcessWarIncome',
+            'CreateAdminNPC',
         ];
         if (!in_array($actionName, $supportedActions, true)) {
             throw new \InvalidArgumentException('unsupported monthly action');