feat(desktop): 确定性昼夜光照过渡与夜灯暖光

新增 lightingBlend 纯函数（黎明明 4:00-6:00、暮色 20:00-22:00 线性过渡，边界与 isNightTick 对齐），天空底色/世界 tint 按混合插值渲染，夜晚灯笼暖光晕强度=LanternGlow（纯叠加矩形、无每帧分配风险）；回归测试含锚点/单调斜坡/确定性/光晕开关。

3 files changed, 85 insertions, 10 deletions

diff --git a/src/LivingVillage.Desktop.Tests/PrototypeTests.fs b/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
index 7e4ce5f..d77abd6 100644
--- a/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
+++ b/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
@@ -670,6 +670,41 @@ type PrototypeTests () =
         Assert.AreEqual<string option>(None, M5Interaction.refreshPrompt world needsView |> fun value -> value.Prompt)
 
     [<TestMethod>]
+    member _.DayPhaseLightingIsPureDeterministicAndTransitionsSmoothly () =
+        let ticksPerHour = Sim.ticksPerDay / 24L
+        let atHour hour = M6Presentation.lightingAtTick (int64 hour * ticksPerHour)
+
+        // Anchors: full day at noon, full night at midnight, no drift.
+        Assert.AreEqual<float32>(0.0f, (atHour 12).Blend)
+        Assert.AreEqual<float32>(1.0f, (atHour 0).Blend)
+        Assert.AreEqual<float32>(1.0f, (atHour 2).Blend)
+
+        // Dawn ramp: 4:00 -> 6:00 goes night -> day, monotonic.
+        let dawnStart = (atHour 4).Blend
+        let dawnMid = (M6Presentation.lightingAtTick (int64 5 * ticksPerHour)).Blend
+        let dawnEnd = (atHour 6).Blend
+        Assert.AreEqual<float32>(1.0f, dawnStart)
+        Assert.AreEqual<float32>(0.5f, dawnMid)
+        Assert.AreEqual<float32>(0.0f, dawnEnd)
+
+        // Dusk ramp 20:00 -> 22:00 goes day -> night monotonically.
+        let duskStart = (atHour 20).Blend
+        let duskMid = (M6Presentation.lightingAtTick (int64 21 * ticksPerHour)).Blend
+        let duskEnd = (atHour 22).Blend
+        Assert.AreEqual<float32>(0.0f, duskStart)
+        Assert.AreEqual<float32>(0.5f, duskMid)
+        Assert.AreEqual<float32>(1.0f, duskEnd)
+
+        // Determinism without randomness.
+        let once = atHour 13
+        let twice = atHour 13
+        Assert.AreEqual<M6RenderProfile>(once, twice)
+
+        // Lantern glow: warm halo only rises with night blend.
+        Assert.AreEqual<float32>(0.0f, (atHour 13).LanternGlow)
+        Assert.AreEqual<float32>(1.0f, (atHour 0).LanternGlow)
+
+    [<TestMethod>]
     member _.WorldPanelDoesNotRenderA永久KeyList () =
         let world = Sim.initialWorldN 42UL 0
         let lines = M5Interaction.panelLines world M5Interaction.initial
diff --git a/src/LivingVillage.Desktop/Game.fs b/src/LivingVillage.Desktop/Game.fs
index 1d50f3d..9464c8b 100644
--- a/src/LivingVillage.Desktop/Game.fs
+++ b/src/LivingVillage.Desktop/Game.fs
@@ -676,6 +676,21 @@ type LivingVillageGame() as this =
                 world.Tick
                 profile.WorldTint
 
+            // Warm lantern glows strengthen as night falls (pure function of tick phase).
+            if profile.LanternGlow > 0.3f then
+                let glow = profile.LanternGlow
+                let haloAlpha = int (90.0f * glow)
+                for prop in renderPlan.Props do
+                    match prop.Kind with
+                    | 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 - 22, screenY - 22, 60, 60), Color(252, 216, 148, int (float32 haloAlpha * 0.35f)))
+                        spriteBatch.Draw(pixel, Rectangle(screenX - 14, screenY - 14, 44, 44), Color(252, 216, 148, haloAlpha))
+                        spriteBatch.Draw(pixel, Rectangle(screenX - 8, screenY - 8, 32, 32), Color(255, 236, 180, haloAlpha))
+                    | _ -> ()
+
             let avatarSpec = VillageArt.avatarSpriteSpec avatarFacing world.Tick
             VillageArt.drawCharacter spriteBatch artTextures camera world.Avatar.Pos avatarSpec profile.WorldTint
 
diff --git a/src/LivingVillage.Desktop/M6Presentation.fs b/src/LivingVillage.Desktop/M6Presentation.fs
index 8e13183..ea8fd2f 100644
--- a/src/LivingVillage.Desktop/M6Presentation.fs
+++ b/src/LivingVillage.Desktop/M6Presentation.fs
@@ -11,7 +11,9 @@ type M6DayNight =
 type M6RenderProfile =
     { Mode: M6DayNight
       Background: Color
-      WorldTint: Color }
+      WorldTint: Color
+      Blend: float32
+      LanternGlow: float32 }
 
 module M6Presentation =
 
@@ -20,15 +22,38 @@ module M6Presentation =
         | Day -> "白天"
         | Night -> "夜晚"
 
-    let profileAtTick (tick: int64) : M6RenderProfile =
-        if Sim.isNightTick tick then
-            { Mode = Night
-              Background = Color(18, 25, 55)
-              WorldTint = Color(118, 136, 184) }
-        else
-            { Mode = Day
-              Background = Color(100, 160, 210)
-              WorldTint = Color(255, 248, 224) }
+    /// Continuous light blend: 0 = full day, 1 = full night. Ramps are deterministic
+    /// pure functions of the simulation tick (dawn 4:00-6:00, dusk 20:00-22:00), so the
+    /// boundaries agree with Sim.isNightTick (night >= 22:00 or < 6:00).
+    let lightingBlend (tick: int64) : float32 =
+        let hourTicks = Sim.ticksPerDay / 24L
+        let hour = float32 (tick / hourTicks)
+        let clamp01 v = if v < 0.0f then 0.0f elif v > 1.0f then 1.0f else v
+        if hour >= 6.0f && hour < 20.0f then 0.0f
+        elif hour >= 22.0f then 1.0f
+        elif hour < 4.0f then 1.0f
+        elif hour < 6.0f then clamp01 (1.0f - (hour - 4.0f) / 2.0f)
+        else clamp01 ((hour - 20.0f) / 2.0f)
+
+    let private lerp (a: int) (b: int) (blend: float32) : int =
+        a + int (float32 (b - a) * blend)
+
+    let backgroundAtBlend (blend: float32) : Color =
+        Color(lerp 100 18 blend, lerp 160 25 blend, lerp 210 55 blend)
+
+    let worldTintAtBlend (blend: float32) : Color =
+        Color(lerp 255 118 blend, lerp 248 136 blend, lerp 224 184 blend)
+
+    /// Pure day-phase lighting: deterministic tint/background plus lantern warm-glow boost.
+    let lightingAtTick (tick: int64) : M6RenderProfile =
+        let blend = lightingBlend tick
+        { Mode = if blend < 0.5f then Day else Night
+          Background = backgroundAtBlend blend
+          Blend = blend
+          WorldTint = worldTintAtBlend blend
+          LanternGlow = blend }
+
+    let profileAtTick (tick: int64) : M6RenderProfile = lightingAtTick tick
 
     let clockLabel (control: SimulationControl) : string =
         if control.Paused then