refactor(core): CORE-02 type emitter maps and fix nested once dispatch

refactor/tasks.json

@@ -770,11 +770,14 @@
         "CORE-01",
         "BASE-03"
       ],
-      "status": "todo",
+      "status": "done",
       "risk": "H",
       "deliverable": "带类型事件映射的原 Emitter 实现",
       "acceptance": "ctx、once/off、重入/异常和链式返回保持",
-      "evidence": []
+      "evidence": [
+        "changes/2026-09-11-CORE-02-typed-emitter.md",
+        "baselines/emitter-validation.json"
+      ]
     },
     {
       "id": "CORE-03",