feat(desktop): 江南氛围标题画面

新增 TitleScreen 纯布局模块（确定性、可测）：五段暮色渐变天幕、黛瓦屋脊/檐口轮廓带（复用图集 8/9 号地块）、水面倒影带（1 号地块）、岸边灯笼光晕、江南水乡四倍大字标题；主菜单改为纵向简洁排布浮于其上，子页面板按内容自适应高度，去除全屏暗色遮罩大黑块。Xvfb 截图像素自查通过。

1 files changed, 39 insertions, 0 deletions

diff --git a/src/LivingVillage.Desktop.Tests/PrototypeTests.fs b/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
index 3e15272..ab7ae1a 100644
--- a/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
+++ b/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
@@ -203,6 +203,45 @@ type PrototypeTests () =
         Assert.IsTrue(first.Tiles |> List.exists (fun tile -> tile.Kind = (VillageArt.StonePaving)))
 
     [<TestMethod>]
+    member _.TitleScreenLayoutIsDeterministicAndLayered () =
+        let first = TitleScreen.layout 1280 720
+        let second = TitleScreen.layout 1280 720
+        Assert.AreEqual<TitleScreen.TitleLayout>(first, second)
+
+        // Title: existing CJK atlas text, large scale, centered headline.
+        Assert.AreEqual<string>("江南水乡", first.TitleText)
+        Assert.AreEqual<int>(4, first.TitleScale)
+
+        // Background must be a layered gradient, never a flat fullscreen block.
+        Assert.IsTrue(first.SkyBands.Length >= 4)
+        Assert.AreEqual<int>(first.SkyBands.Length, first.SkyBands |> List.distinct |> List.length)
+
+        // Skyline reuses the Jiangnan roof tiles (ridge=8, eave=9) across the full width.
+        let roofSlots = TitleScreen.roofSlots
+        Assert.AreEqual<int>(8, fst roofSlots)
+        Assert.AreEqual<int>(9, snd roofSlots)
+        Assert.AreEqual<int>(1280 / 32, first.RoofTileSlots.Length)
+        Assert.IsTrue(first.RoofTileSlots |> List.forall (fun slot -> slot = 8 || slot = 9))
+        Assert.IsTrue(first.RoofTileSlots |> List.contains 8)
+        Assert.IsTrue(first.RoofTileSlots |> List.contains 9)
+
+        // Water band reuses the water tile slot and anchors the lantern row.
+        Assert.AreEqual<int>(1, TitleScreen.waterSlot)
+        Assert.AreEqual<int>(2, first.WaterRows.Length)
+        Assert.IsTrue(first.Lanterns.Length >= 3)
+        let lanternColor, lanternHalo = TitleScreen.lanternColors
+        Assert.AreEqual<int>(212, lanternColor.R)
+        Assert.AreEqual<int>(92, lanternColor.G)
+        Assert.AreEqual<int>(74, lanternColor.B)
+        Assert.IsTrue(lanternHalo.R > lanternColor.R && lanternHalo.G > lanternColor.G)
+
+        // Menu items form one vertical column below the title.
+        Assert.IsTrue(first.MenuTopY > first.TitleY)
+        Assert.IsTrue(first.MenuLineHeight > 0)
+        Assert.IsTrue(first.PanelX + first.PanelWidth <= 1280)
+        Assert.IsTrue(first.PanelY + first.PanelHeight <= 720)
+
+    [<TestMethod>]
     member _.NpcVariantsAreStableAndAnimationCoversFourDirectionsAndTwoFrames () =
         let sameNpc = npcVisualVariant (NpcId 7)
         let repeatedNpc = npcVisualVariant (NpcId 7)