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.

app/api/v1/endpoints/simulation.py

@@ -180,6 +180,9 @@ def valve_isolation_endpoint(
     network: str = Query(..., description="管网名称（或数据库名称）"),
     accident_element: List[str] = Query(..., description="发生事故的管段/节点ID列表"),
     disabled_valves: List[str] = Query(None, description="已故障的阀门ID列表（可选）"),
+    accident_element_type: Literal["auto", "link", "node"] = Query(
+        "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",
+    ),
 ):
     """
     阀门隔离分析
@@ -187,13 +190,19 @@ def valve_isolation_endpoint(
     - **network**: 管网名称（或数据库名称）
     - **accident_element**: 发生事故的管段/节点ID列表
     - **disabled_valves**: 已故障的阀门ID列表（可选）
+    - **accident_element_type**: auto优先管段；link仅匹配管段；node仅匹配节点
     
     返回隔离方案，包括：
     - must_close_valves: 必须关闭的阀门列表
     - optional_valves: 可选关闭的阀门列表
-    - affected_nodes: 受影响的节点列表；不可隔离时为空列表
-    - affected_node_count: 受影响的节点总数
-    - isolatable: 是否可以有效隔离
+    - affected_nodes / affected_node_count: 最近阀门围成的直接隔离区；不可隔离时列表为空，计数保留
+    - supply_affected_nodes / supply_affected_node_count: 按建议关阀后新增失去水源连接的节点；未验证或不可隔离时为null
+    - source_check_performed: 是否已执行水源连通检查
+    - isolation_failure_reason: 不可隔离原因；可隔离时为null
+    - isolatable: 存在关阀边界，且直接隔离区不再连通任何水源
+
+    使用模型初始开关状态进行无向拓扑分析，水池按潜在水源处理。
+    不包含时变控制、水池蓄水量或压力流量计算，不是现场停水范围的水力证明。
     """
     # result = {
     #     "accident_element": "P461309",
@@ -212,7 +221,13 @@ def valve_isolation_endpoint(
     #     "must_close_valves": ["210521658", "V12974", "V12986", "V12993"],
     #     "optional_valves": [],
     # }
-    result = analyze_valve_isolation(network, accident_element, disabled_valves)
+    try:
+        result = analyze_valve_isolation(
+            network, accident_element, disabled_valves,
+            accident_element_type=accident_element_type,
+        )
+    except ValueError as exc:
+        raise HTTPException(status_code=422, detail=str(exc)) from exc
     return result