fix: planner formation lane offset + add 3-drone integration test

Bug: planner used symmetric lane offset (Z=-50/0/+50) but DroneEntity uses start-anchored (Z=0/50/100). 3rd drone at Z=100 got no clouds.

Fix: planner laneOffset = yLane * laneSpacing (matches DroneEntity formationIndex * lateralSpacing).

Test: Scenario_3DronesFormation - 3 drones in Formation (Z=0/50/100), 3 fire units, all destroyed. 192 tests pass.

src/CounterDrone.Core/Algorithms/DefensePlanner.cs

@@ -401,11 +401,13 @@ namespace CounterDrone.Core.Algorithms
             float midArc = RouteGeometry.ArcLengthNearestTo(wps, mid.X, mid.Z);
             float crossArc = midArc + targetOffset;
 
-            // 编队横向偏移：按车道分布在航路法向上
+            // 编队横向偏移：按车道分布在航路法向上，与 DroneEntity 编队偏移一致（起点展开）。
+            // DroneEntity: latOffset = formationIndex * lateralSpacing（0/50/100...）
             // 法向 = 切向旋转 90°，用 RouteGeometry.TangentAt 取穿越点处航路方向
             var (tanX, tanZ) = RouteGeometry.TangentAt(wps, crossArc);
             float normalX = -tanZ, normalZ = tanX; // 切向逆时针 90° = 左侧法向
-            float laneOffset = yLanes > 1 ? (yLane - (yLanes - 1) / 2f) * (formationWidth / Math.Max(1, yLanes - 1)) : 0f;
+            float laneSpacing = yLanes > 1 ? formationWidth / Math.Max(1, yLanes - 1) : 0f;
+            float laneOffset = yLane * laneSpacing;
 
             // 穿越点 = 航路上 crossArc 处 + 横向车道偏移
             var (routeX, routeY, routeZ) = RouteGeometry.PositionAt(wps, crossArc);

test/unit/CounterDrone.Core.Tests/FullPipelineTests.cs

@@ -483,5 +483,60 @@ namespace CounterDrone.Core.Tests
             Assert.True(drone.Hp < 0.1f, msg);
             VerifyAndExportReport(eng, drone);
         }
+
+        // ═══════════════════════════════════════════════
+        // 场景 6：3 架活塞编队（横排 Z=0/50/100）— 多无人机端到端
+        //   验证 planner 给每个车道分配云团、3 架都被击毁
+        // ═══════════════════════════════════════════════
+
+        [Fact]
+        public void Scenario_3DronesFormation_AllDestroyed()
+        {
+            var task = _scenario.CreateTask("3架编队拦截测试", "");
+            _taskId = task.Id;
+
+            _scenario.SaveScene(_taskId, new CombatScene { WindSpeed = 0 });
+            _scenario.SaveTarget(_taskId, new TargetConfig
+            {
+                GroupId = "default", TargetType = (int)TargetType.Piston,
+                PowerType = (int)PowerType.Piston,
+                Quantity = 3,
+                TypicalSpeed = 200, TypicalAltitude = 500,
+            });
+            // 3 架横排编队：Formation 模式，横向间距 50m
+            // 引擎会生成 3 架无人机，Z 偏移 0/50/100（latIdx × LateralSpacing）
+            _scenario.SaveRoute(_taskId, "default", new RoutePlan
+            {
+                FormationMode = (int)FormationMode.Formation,
+                LateralSpacing = 50,
+                LateralCount = 3,
+                LongitudinalCount = 1,
+            },
+                new List<Waypoint>
+                {
+                    new Waypoint { PosX = 0, PosY = 500, PosZ = 0, Speed = 200 },
+                    new Waypoint { PosX = 10000, PosY = 500, PosZ = 0, Speed = 200 },
+                });
+            // 3 个火力单元部署在中点附近（X=4500，每个单元 i*50 偏移 → 4500/4550/4600）
+            _scenario.SaveDeployment(_taskId, new List<EquipmentDeployment>
+            {
+                MakeEquipment(DefaultFireUnits.GetById("ground-light"), AerosolType.InertGas, 3, 4500, 0, 50),
+            });
+            _scenario.SaveCloudDispersal(_taskId, new CloudDispersal { AerosolType = (int)AerosolType.InertGas, DisperseHeight = 500 });
+
+            var eng = RunSimulation(8000);
+            var launched = eng.Events.Count(e => e.Type == SimEventType.MunitionLaunched);
+            var clouds = eng.Events.Count(e => e.Type == SimEventType.CloudGenerated);
+            var destroyed = eng.Events.Count(e => e.Type == SimEventType.DroneDestroyed);
+
+            // 验证：3 架无人机都被击毁
+            var msg = $"3Drones: launched={launched} clouds={clouds} destroyed={destroyed} drones={eng.Drones.Count}";
+            foreach (var d in eng.Drones)
+                msg += $" [{d.Status} hp={d.Hp:F2} pos=({d.PosX:F0},{d.PosZ:F0})]";
+            VerifyAndExportReport(eng, eng.Drones[0]);
+            Assert.Equal(3, eng.Drones.Count);
+            Assert.True(launched > 0, msg);
+            Assert.True(eng.Drones.All(d => d.Status == DroneStatus.Destroyed), msg);
+        }
     }
 }