feat(investigations): add event impact and work-order feedback flows

Add isolated burst and pollution impact evidence, parallel work-order workflows, persisted notifications and graph updates.

Checkpoint current code. Known follow-ups remain for large pollution result previews and graceful geometry failure.

app/mcp/analysis_models.py

@@ -97,6 +97,23 @@ class BurstLocationInput(CalculationInput):
         return self
 
 
+class ContaminantSourceTraceInput(CalculationInput):
+    candidate_node_ids: list[Id] = Field(min_length=1, max_length=20,
+        description="根据事件位置、附近资产或水质设备映射取得的候选模型节点；Server核验节点存在后稳定返回一个候选。当前为临时定位接口，尚未执行污染反演")
+    start: datetime = Field(description="带时区的事件核查窗口开始")
+    end: datetime = Field(description="带时区的事件核查窗口结束")
+
+    @model_validator(mode="after")
+    def valid_window(self):
+        if self.start.tzinfo is None or self.end.tzinfo is None:
+            raise ValueError("timestamps require explicit timezone")
+        if not timedelta(0) < self.end - self.start <= timedelta(days=1):
+            raise ValueError("window must be positive and at most 24 hours")
+        if len(set(self.candidate_node_ids)) != len(self.candidate_node_ids):
+            raise ValueError("candidate_node_ids must be distinct")
+        return self
+
+
 class ValveIsolationInput(CalculationInput):
     accident_element: list[Id] = Field(min_length=1, max_length=20, description="经核实或明确作为候选的事故管段/节点ID")
     accident_element_type: Literal["auto", "link", "node"] = Field(default="auto", description="事故要素类型；auto优先识别管段，再识别节点；节点与管段重号时，节点分析须指定node，纯管段分析可指定link")
@@ -143,6 +160,10 @@ class ContaminantSimulationInput(ScenarioInput):
     source: Id = Field(description="假设污染源节点；这是正向传播模拟，结果按给定源解释")
     concentration: float = Field(gt=0, allow_inf_nan=False, description="假设源浓度，mg/L")
     pattern: Id | None = Field(default=None, description="已存在的污染源时间模式ID；省略时采用持续恒定源")
+    include_impact_coverage: bool = Field(default=False, strict=True,
+        description="估计处置前的污染传播范围；在筛选展示节点前汇总全网节点整个模拟时段的浓度，保存影响节点、首个超过阈值的报告时刻、峰值及地图覆盖")
+    impact_threshold_mg_l: float = Field(default=0, ge=0, allow_inf_nan=False,
+        description="模型影响范围的浓度阈值，mg/L，按严格大于判定；默认0表示模型中出现正浓度，仅为情景展示条件，不是饮用水安全限值。沿用模型初始水质与反应条件")
 
 
 class ValveClosureInput(ScenarioInput):