fix(isolation): distinguish accident links from same-numbered nodes

Prefer link endpoints for legacy accident IDs and allow explicit node selection. Read authoritative initial statuses and sources, verify source isolation, and separate direct isolation from newly disconnected supply nodes. Return validation errors as HTTP 422.

The node-first lookup misrouted adjacent Fengyang pipes 19025 and 19026 into unrelated regions. Regression cases fail against the previous algorithm and pass after this change.

contracts/manifest.json

@@ -3,7 +3,7 @@
   "contracts": {
     "server": {
       "file": "server-v1.openapi.json",
-      "sha256": "b565d841061c9091f48ff3118bcc0cbb1b918b0cb8c2316d177570e8b2d8ba29"
+      "sha256": "5b8ec0b469f1194e72214003a9cf427489f48de19ae31ee6492821cf64916b6d"
     }
   }
 }

contracts/server-v1.openapi.json

@@ -35969,6 +35969,23 @@
               "type": "array"
             }
           },
+          {
+            "description": "事故要素类型；auto优先管段再节点；分析同名节点须指定node，纯管段分析可指定link",
+            "in": "query",
+            "name": "accident_element_type",
+            "required": false,
+            "schema": {
+              "default": "auto",
+              "description": "事故要素类型；auto优先管段再节点；分析同名节点须指定node，纯管段分析可指定link",
+              "enum": [
+                "auto",
+                "link",
+                "node"
+              ],
+              "title": "Accident Element Type",
+              "type": "string"
+            }
+          },
           {
             "in": "header",
             "name": "X-Project-Id",