fix(desktop): P19 白天色调去偏黄（day tint 中性白平衡，黄昏暖橙保留）p19-daylight-taming

3 files changed, 35 insertions, 4 deletions

diff --git a/src/LivingVillage.Desktop.Tests/DesktopTests.fs b/src/LivingVillage.Desktop.Tests/DesktopTests.fs
index 00e445b..b78f4e0 100644
--- a/src/LivingVillage.Desktop.Tests/DesktopTests.fs
+++ b/src/LivingVillage.Desktop.Tests/DesktopTests.fs
@@ -143,6 +143,23 @@ type DesktopTests () =
         Assert.IsTrue(day.WorldTint.G > day.WorldTint.B)
 
     [<TestMethod>]
+    member _.NoonLightingIsWarmthFreeWithNeutralWhiteBalance () =
+        let noonTick = 12L * Sim.ticksPerDay / 24L
+        let noon = M6Presentation.profileAtTick noonTick
+
+        Assert.AreEqual<M6DayNight>(Day, noon.Mode)
+        Assert.AreEqual<float32>(0.0f, noon.SkyWarmth)
+        Assert.AreEqual<float32>(0.0f, noon.LanternGlow)
+        Assert.AreEqual<int>(0, M6Presentation.goldenVeilAlpha noonTick)
+        // P19 offender was the day world tint attenuating blue (255/248/224); it is neutral now.
+        Assert.AreEqual<int>(255, int noon.WorldTint.R)
+        Assert.AreEqual<int>(int noon.WorldTint.R, int noon.WorldTint.G)
+        Assert.AreEqual<int>(int noon.WorldTint.G, int noon.WorldTint.B)
+        // The sky stays a plain blue, never warm.
+        Assert.IsTrue(noon.Background.B > noon.Background.G)
+        Assert.IsTrue(noon.Background.B > noon.Background.R)
+
+    [<TestMethod>]
     member _.DaylightAutoplayBootstrapStartsAtDawnAndPreservesDefaultStart () =
         let dawnTick = 6L * Sim.ticksPerDay / 24L
         let daylightWorld = WorldBootstrap.initialWorldForDaylight true 42UL Sim.npcCount
diff --git a/src/LivingVillage.Desktop.Tests/PrototypeTests.fs b/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
index 895dff8..e58139c 100644
--- a/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
+++ b/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
@@ -897,6 +897,18 @@ type PrototypeTests () =
         Assert.IsTrue(warmDusk.Background.B < (M6Presentation.backgroundAtBlend warmDusk.Blend).B)
         Assert.IsTrue(warmDusk.WorldTint.R > (M6Presentation.worldTintAtBlend warmDusk.Blend).R)
         Assert.IsTrue(warmDusk.WorldTint.B < (M6Presentation.worldTintAtBlend warmDusk.Blend).B)
+
+        // P19: no daylight warm cast. Noon (and the whole 10:00-15:00 plateau) must be warmth-free
+        // and channel-neutral, so the world renders at a true white balance instead of yellow.
+        for hour in 10 .. 15 do
+            let daylight = atHour hour
+            Assert.IsTrue(abs (daylight.SkyWarmth) < 1e-6f, sprintf "hour %d must carry no warmth" hour)
+            Assert.IsTrue((int daylight.WorldTint.R) = (int daylight.WorldTint.G), sprintf "hour %d world tint must be neutral" hour)
+            Assert.IsTrue((int daylight.WorldTint.G) = (int daylight.WorldTint.B), sprintf "hour %d world tint must be neutral" hour)
+            Assert.IsTrue((M6Presentation.goldenVeilAlpha (int64 hour * ticksPerHour)) = 0, sprintf "hour %d must have no golden veil" hour)
+            Assert.IsTrue(abs (daylight.LanternGlow) < 1e-6f, sprintf "hour %d must have no lantern glow" hour)
+        let noon = atHour 12
+        Assert.IsTrue((int noon.WorldTint.R) = 255, "neutral day tint should be full white (no attenuation)")
         // Additive veil: positive and strongest at the golden peaks, zero at noon/midnight.
         Assert.AreEqual<int>(0, M6Presentation.goldenVeilAlpha (int64 12 * ticksPerHour))
         Assert.AreEqual<int>(0, M6Presentation.goldenVeilAlpha 0L)
diff --git a/src/LivingVillage.Desktop/M6Presentation.fs b/src/LivingVillage.Desktop/M6Presentation.fs
index 25737d7..90d2e65 100644
--- a/src/LivingVillage.Desktop/M6Presentation.fs
+++ b/src/LivingVillage.Desktop/M6Presentation.fs
@@ -76,13 +76,15 @@ module M6Presentation =
             lerp 160 25 blend + int (20.0f * warmth),
             lerp 210 55 blend - int (90.0f * warmth))
 
-    /// World tint also warms (red up, green slightly down, blue down) so tiles, props and
-    /// characters all lean golden before the additive veil is layered on top.
+    /// World tint multiplies the whole scene. The day baseline is neutral white so noon keeps
+    /// a true white balance (the old day base 255/248/224 clipped blue by ~12% and made daylight
+    /// look yellow); night stays cool, and the golden shade only appears through `warmth`, which
+    /// is a pure function that is zero at noon and outside the dawn/dusk windows.
     let worldTintAtWarmth (blend: float32) (warmth: float32) : Color =
         Color(
             lerp 255 118 blend + int (70.0f * warmth),
-            lerp 248 136 blend - int (10.0f * warmth),
-            lerp 224 184 blend - int (75.0f * warmth))
+            lerp 255 136 blend - int (10.0f * warmth),
+            lerp 255 184 blend - int (75.0f * warmth))
 
     /// Warmth-free base colours (kept for callers that only have a blend value).
     let backgroundAtBlend (blend: float32) : Color = backgroundAtWarmth blend 0.0f