feat(desktop): 江南水乡河道横贯与波纹两帧

场景改为沿村蜿蜒水带（北岸凸湾、中段横贯、南段收窄），南北两岸石板路沿河展开，木桥三块纵跨全河连接民居门前石径；水面新增第二张波纹图块，按世界 tick/32 取模确定性交替，绘制无新增每帧分配。

1 files changed, 36 insertions, 2 deletions

diff --git a/src/LivingVillage.Desktop.Tests/PrototypeTests.fs b/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
index 06b3250..7959d27 100644
--- a/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
+++ b/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
@@ -301,8 +301,42 @@ type PrototypeTests () =
             Assert.IsTrue(footprint.Contains({ X = door.X + dx; Y = door.Y - 2 } : TilePosition), sprintf "missing ridge tile dx=%d" dx)
             Assert.IsTrue(footprint.Contains({ X = door.X + dx; Y = door.Y - 1 } : TilePosition), sprintf "missing eave tile dx=%d" dx)
             Assert.IsTrue(footprint.Contains({ X = door.X + dx; Y = door.Y } : TilePosition), sprintf "missing wall tile dx=%d" dx)
-        // 12 house tiles + 2 bridge + 3 bamboo + 2 garden.
-        Assert.AreEqual<int>(19, footprint.Count)
+        // 12 house tiles + 3 bridge + 3 bamboo + 2 garden.
+        Assert.AreEqual<int>(20, footprint.Count)
+
+    [<TestMethod>]
+    member _.WaterRippleFramesAreDeterministicAndTwoPhase () =
+        Assert.AreEqual<int>(0, VillageArt.waterFrameTick 0L)
+        Assert.AreEqual<int>(0, VillageArt.waterFrameTick 31L)
+        Assert.AreEqual<int>(1, VillageArt.waterFrameTick 32L)
+        Assert.AreEqual<int>(1, VillageArt.waterFrameTick 63L)
+        Assert.AreEqual<int>(0, VillageArt.waterFrameTick 64L)
+        Assert.AreEqual<int>(VillageArt.waterFrameTick 100L, VillageArt.waterFrameTick 100L)
+
+    [<TestMethod>]
+    member _.RiverBandSpansTheSceneWithBankPathsAndCrossing () =
+        let plan = VillageArt.sampleRenderPlan ()
+        let footprintOf (value: VillageArt.JiangnanRenderPlan) = VillageArt.planFootprint value
+        let waters = plan.Grounds |> List.filter (fun (_, kind) -> kind = VillageArt.Water) |> List.map fst |> Set.ofList
+        let paths = plan.Grounds |> List.filter (fun (_, kind) -> kind = VillageArt.StonePath) |> List.map fst |> Set.ofList
+        let door = scene.Homes |> List.head |> fun home -> home.Door
+
+        // The river must run the full width of the decorated scene as a readable water band.
+        Assert.AreEqual<int>(20, [ 0 .. 19 ] |> List.filter (fun x -> waters.Contains({ X = x; Y = 12 } : TilePosition)) |> List.length)
+        Assert.IsTrue(waters.Contains({ X = 6; Y = 13 } : TilePosition))
+        // Banks stay walkable stone, and the door row connects to the north bank.
+        for x in 0 .. 19 do
+            if x <> 6 && x <> 7 && x <> 8 then
+                Assert.IsTrue(paths.Contains({ X = x; Y = 11 } : TilePosition), sprintf "missing north bank x=%d" x)
+        for y in 6 .. 10 do
+            Assert.IsTrue(paths.Contains({ X = 6; Y = y } : TilePosition), sprintf "missing door connector y=%d" y)
+        // Bridge footprint crosses the full river between the banks.
+        let bridge = plan.Props |> List.find (fun prop -> prop.Kind = VillageArt.Bridge)
+        let expectedBridge : TilePosition = { X = 6; Y = 11 }
+        Assert.AreEqual<TilePosition>(expectedBridge, bridge.Position)
+        for y in 11 .. 13 do
+            let bridgeTile = VillageArt.worldTile plan { X = 6; Y = y }
+            Assert.IsTrue(footprintOf plan |> List.contains bridgeTile, sprintf "bridge tile y=%d" y)
 
     [<TestMethod>]
     member _.FacingUsesTheActualMovementOrTargetVector () =