docs: add M2 soak-test scenario matrix and data manifest

Records the human decision to test against the real gateway with real
data instead of building a mock gateway, six execution scenarios with
fault-source mixing, hard invariants scored from our own telemetry,
and the corpus inventory pulled from the lab server.

research-wiki/graph/edges.json

@@ -15,6 +15,11 @@
       "id": "metric:call-telemetry-coverage",
       "label": "每次调用必录覆盖率(含缓存命中/失败/取消)",
       "type": "metric"
+    },
+    {
+      "id": "finding:m2-soak-workload",
+      "label": "M2 真实数据压测: 场景矩阵与数据清单",
+      "type": "finding"
     }
   ],
   "links": [