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.

contracts/server-v1.openapi.json

@@ -3739,9 +3739,17 @@
             "type": "array"
           },
           "label": {
-            "minLength": 1,
-            "title": "Label",
-            "type": "string"
+            "anyOf": [
+              {
+                "minLength": 1,
+                "type": "string"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Required for a new node. Omit or use null to retain an existing node's label. Use the same node_id to revise status or detail without adding another step.",
+            "title": "Label"
           },
           "map_targets": {
             "items": {
@@ -3777,8 +3785,7 @@
           }
         },
         "required": [
-          "node_id",
-          "label"
+          "node_id"
         ],
         "title": "InvestigationGraphNodeUpdate",
         "type": "object"
@@ -5160,7 +5167,8 @@
               "access_approval_pending",
               "action_approval_pending",
               "human_input_required",
-              "external_coordination_failed"
+              "external_coordination_failed",
+              "work_order_feedback"
             ],
             "title": "Kind",
             "type": "string"
@@ -5295,6 +5303,26 @@
             "minimum": 1.0,
             "title": "Version",
             "type": "integer"
+          },
+          "work_order_action": {
+            "anyOf": [
+              {
+                "$ref": "#/components/schemas/HumanApprovalAction"
+              },
+              {
+                "type": "null"
+              }
+            ]
+          },
+          "work_order_reference": {
+            "anyOf": [
+              {
+                "$ref": "#/components/schemas/WorkOrderNotificationReference"
+              },
+              {
+                "type": "null"
+              }
+            ]
           }
         },
         "required": [
@@ -7431,7 +7459,8 @@
           "metric": {
             "enum": [
               "pressure",
-              "flow"
+              "flow",
+              "quality"
             ],
             "title": "Metric",
             "type": "string"
@@ -9712,6 +9741,7 @@
                   "cancel_task_run",
                   "run_simulation",
                   "run_contaminant_simulation",
+                  "run_contaminant_source_trace",
                   "analyze_valve_closure",
                   "analyze_flushing",
                   "analyze_pressure_regulation",
@@ -11130,6 +11160,53 @@
         "title": "WorkOrderDraftUpdateCommand",
         "type": "object"
       },
+      "WorkOrderNotificationReference": {
+        "additionalProperties": false,
+        "properties": {
+          "evidence_id": {
+            "anyOf": [
+              {
+                "minLength": 1,
+                "type": "string"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "title": "Evidence Id"
+          },
+          "source_event_id": {
+            "minLength": 1,
+            "title": "Source Event Id",
+            "type": "string"
+          },
+          "source_revision": {
+            "minimum": 1.0,
+            "title": "Source Revision",
+            "type": "integer"
+          },
+          "status": {
+            "enum": [
+              "scheduled",
+              "assigned",
+              "in_progress",
+              "awaiting_feedback",
+              "completed",
+              "cancelled",
+              "failed"
+            ],
+            "title": "Status",
+            "type": "string"
+          }
+        },
+        "required": [
+          "source_event_id",
+          "source_revision",
+          "status"
+        ],
+        "title": "WorkOrderNotificationReference",
+        "type": "object"
+      },
       "WorkbenchAlertSource": {
         "additionalProperties": false,
         "properties": {