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

4 files changed, 62 insertions, 4 deletions

diff --git a/docs/维护说明.md b/docs/维护说明.md
index 14d11f6..b22c6bf 100644
--- a/docs/维护说明.md
+++ b/docs/维护说明.md
@@ -227,6 +227,24 @@ dotnet src/LivingVillage.Headless/bin/Release/net8.0/LivingVillage.Headless.dll
 - 门槛：clean rebuild 0 警告 0 错误；`final_digest=953775FAEB2FDDE97289491AA260BD8D390C571E48A7A13AD2CB6FB7124F7F6C`
   一致、`performance_determinism=PASS`。
 
+## P19 批验：白天偏黄过曝治理（daylight 色调路径）
+
+- line-level 定位：offender 唯一是 `M6Presentation.worldTintAtWarmth`（`M6Presentation.fs:81-87`）的 **day 基线**
+  —— `lerp 248 136 blend`（:84）与 `lerp 224 184 blend`（:85）在 `blend=0`（正午）仍给出 `(255,248,224)`：蓝通道
+  被压约 12%，整场景乘性偏黄。黄昏暖色链在白天并不生效，已逐一排除：`transitionWarmth`（:51-60）bump 仅在
+  4.0–6.5 与 19.25–21.75；`goldenVeilAlpha`（:65）正午 = 0；`LanternGlow = max blend (warmth*0.8)`（:101）
+  正午 = 0；`lightingBlend`（:36-43）正午 = 0。故「白天偏黄」= day world-tint 基线，与黄昏暖窗无关。
+- 修复：day 基线改中性白 `(255,255,255)`，乘性恒等（geometry 保留 true white balance，无伪色彩）；night 基线
+  `(118,136,184)` 与 `warmth` 暖移不变，黄昏/清晨暖橙完全保留。
+- 回归：新增 `NoonLightingIsWarmthFreeWithNeutralWhiteBalance`（DesktopTests）；PrototypeTests 增白天
+  10:00–15:00 平台断言（warmth=0、通道中性、veil=0、glow=0）；Desktop 108→109，Kernel 89 不变。
+- 证据：`/tmp/opencode/lv-p19-art/`（`p19-noon-12h-0{1,2}.png`、`p19-dusk-20h45-01.png`、
+  `p19-night-00h30-01.png`、`p19-before-noon-yellow.png` vs `p19-after-noon-neutral.png`）。画面均值：
+  正午前 `(71,109,66)` R−B=+5.1（偏黄）→ 正午后 `(70,109,75)` R−B=−5.3（中性）；黄昏 `(146,113,61)`
+  R−B=+85（暖橙保留）；深夜 `(34,60,56)` 冷调；白块回归 0 命中。
+- 门槛：clean rebuild 0 警告 0 错误；`final_digest=953775FAEB2FDDE97289491AA260BD8D390C571E48A7A13AD2CB6FB7124F7F6C`
+  一致、`performance_determinism=PASS`。
+
 ## 已验证命令
 
 ```bash
@@ -265,6 +283,13 @@ for pair in day:12.0 dusk:20.75 night:0.0; do name=${pair%%:*}; hour=${pair##*:}
     LV_AUTOPLAY_START_HOUR=$hour LV_AUTOPLAY_RECORD=1 \
     LV_RECORD_DIR=/tmp/opencode/lv-p17-art/$name LV_RECORD_EVERY=2 \
     dotnet src/LivingVillage.Desktop/bin/Release/net8.0/LivingVillage.Desktop.dll; done
+# P19 白天色温取证（正午 12 / 黄昏 20.75 / 深夜 0.5 三帧对比）
+for pair in noon:12.0 dusk:20.75 night:0.5; do name=${pair%%:*}; hour=${pair##*:}; \
+  timeout 100 xvfb-run -a -s "-screen 0 1280x720x24" env LV_AUTOPLAY_SAMPLE=1 \
+    LV_AUTOPLAY_START_HOUR=$hour LV_AUTOPLAY_RECORD=1 \
+    LV_RECORD_DIR=/tmp/opencode/lv-p19-art/$name LV_RECORD_EVERY=2 \
+    dotnet src/LivingVillage.Desktop/bin/Release/net8.0/LivingVillage.Desktop.dll; done
+
 # P18 黄昏暖色取证（20:45 真实帧；深夜把 20.75 换成 0）
 timeout 100 xvfb-run -a -s "-screen 0 1280x720x24" env LV_AUTOPLAY_SAMPLE=1 \
   LV_AUTOPLAY_START_HOUR=20.75 LV_AUTOPLAY_RECORD=1 \
@@ -304,6 +329,8 @@ python3 scripts/check-no-white-blocks.py evidence/night-run
 - `/tmp/opencode/lv-p13/evidence/`（P13：`walk-idle-frames.png`、`water-3phase.png`、
   `smoke-3phase.png`、`water-2frame.png`、`smoke-2frame.png`、`day-panorama.png`、
   `night-lantern.png`、`day-night-compare.png`、`walk-real-run.png`、`day-run/`、`night-run/`）
+- `/tmp/opencode/lv-p19-art/`（P19：`p19-noon-12h-0{1,2}.png`、`p19-dusk-20h45-01.png`、
+  `p19-night-00h30-01.png`、`p19-before-noon-yellow.png`/`p19-after-noon-neutral.png`；同一份拷入 `evidence/`）
 - `/tmp/opencode/lv-p18-art/`（P18：`p18-dusk-20h45-0{1,2}.png`、`p18-night-deep-01.png`、
   `p18-before-old-dusk-blue.png`/`p18-after-new-dusk-warm.png`、`sample-dusk.mp4`；同一份拷入 `evidence/`）
 - `/tmp/opencode/lv-p17-art/`（P17：`p17-day-12h-0{1,2}.png`、`p17-dusk-20h45-0{1,2}.png`、
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