fix(desktop): 灯笼光晕按自身 alpha 预乘并改径向层叠，消除夜间纯白方块

- 新增 VillageArt.premultiply：MonoGame SpriteBatch 默认预乘混合，直传
  Color(r,g,b,a) 会直接加 rgb 导致多层暖色饱和成 75x75 纯白块
- lanternGlowLayers 用同心圆 pixel run 做径向衰减，逐层预乘，只在
  RiverLantern 实体处绘制
- 水面相位改 waterFrameTickAt=(tick/32+x+2y)%3，同一帧相邻砖相位不同
- 炊烟改为 drawWorld 末尾独立一遍，位置 offsetTile 0 -3，画在屋瓦/竹子之上
- 角色脚底对齐 characterFeetOffset=16 并加预乘椭圆接触阴影
- 补全 Interaction.itemName 的 ItemKind 匹配（否则非 Food 交易会崩溃且告警）

1 files changed, 10 insertions, 10 deletions

diff --git a/src/LivingVillage.Desktop/Game.fs b/src/LivingVillage.Desktop/Game.fs
index c91fe6e..6918e00 100644
--- a/src/LivingVillage.Desktop/Game.fs
+++ b/src/LivingVillage.Desktop/Game.fs
@@ -741,28 +741,28 @@ type LivingVillageGame() as this =
                 profile.WorldTint
 
             // Warm lantern glows strengthen as night falls (pure function of tick phase).
-            // Soft radial falloff made of wide translucent rings; no hot white core,
-            // the lantern sprite itself stays readable underneath.
+            // Concentric premultiplied circles fall off radially from each lantern tile, so
+            // the core stays a soft warm disc instead of saturating into a white block, and
+            // no glow is painted where there is no lantern entity.
             if profile.LanternGlow > 0.3f then
                 let glow = profile.LanternGlow
-                let haloAlpha = int (34.0f * glow)
-                let ringAlpha = int (18.0f * glow)
+                let peakAlpha = int (140.0f * glow)
                 for prop in renderPlan.Props do
                     match prop.Kind with
                     | VillageArt.RenderPropKind.RiverLantern ->
                         let position = VillageArt.worldTile renderPlan prop.Position
-                        let screenX = position.X * Sim.tilePixels - int camera.X + Sim.tilePixels / 2
-                        let screenY = position.Y * Sim.tilePixels - int camera.Y - Sim.tilePixels / 2
-                        spriteBatch.Draw(pixel, Rectangle(screenX - 30, screenY - 30, 76, 76), Color(252, 196, 128, int (float32 ringAlpha * 0.5f)))
-                        spriteBatch.Draw(pixel, Rectangle(screenX - 24, screenY - 24, 64, 64), Color(252, 206, 148, ringAlpha))
-                        spriteBatch.Draw(pixel, Rectangle(screenX - 18, screenY - 18, 52, 52), Color(252, 216, 148, haloAlpha))
-                        spriteBatch.Draw(pixel, Rectangle(screenX - 12, screenY - 12, 40, 40), Color(255, 226, 168, haloAlpha))
+                        let centerX = position.X * Sim.tilePixels - int camera.X + Sim.tilePixels / 2
+                        let centerY = position.Y * Sim.tilePixels - int camera.Y + Sim.tilePixels / 2
+                        for (rect, color) in VillageArt.lanternGlowLayers centerX centerY 44 6 255 214 150 peakAlpha do
+                            spriteBatch.Draw(pixel, rect, color)
                     | _ -> ()
 
+            VillageArt.drawGroundShadow spriteBatch pixel camera world.Avatar.Pos
             let avatarSpec = VillageArt.avatarSpriteSpec avatarFacing avatarMoving world.Tick
             VillageArt.drawCharacter spriteBatch artTextures camera world.Avatar.Pos avatarSpec profile.WorldTint
 
             for npc in world.Npcs do
+                VillageArt.drawGroundShadow spriteBatch pixel camera npc.Pos
                 let spec = VillageArt.npcSpriteSpecAtTarget npc.Id npc.Pos npc.Mind.Target world.Tick
                 VillageArt.drawCharacter spriteBatch artTextures camera npc.Pos spec profile.WorldTint
         spriteBatch.End()