p74: 启动开场过渡（水墨式渐显）+ 开始界面布局回归

新增纯函数 InkReveal.fs（inkStrength ease-out 消散 + 6 滴预乘墨滴 dabs），DrawSplash 在场景层之上、标题之下绘制，与既有 reveal/veil 淡入叠加，形成可辨识水墨开场；单滴 alpha<255 且椭圆行落成，无实心黑块。开始界面沿用既有 开始/读档/退出（有档 继续）。新增 P74LaunchTransitionTests（4 例）与 LV_P74_SHOT/-analyze-p74 证据（5 帧墨幕非增、两两 diff>0，verdict=PASS）。HUD 结构未动；Desktop 350/350、Kernel 120/120、digest 与 p70 一致。

1 files changed, 29 insertions, 0 deletions

diff --git a/src/LivingVillage.Desktop/Game.fs b/src/LivingVillage.Desktop/Game.fs
index 3d04ca7..a4f994b 100644
--- a/src/LivingVillage.Desktop/Game.fs
+++ b/src/LivingVillage.Desktop/Game.fs
@@ -319,6 +319,10 @@ type LivingVillageGame() as this =
     let p42ShotMode = Environment.GetEnvironmentVariable("LV_P42_SHOT") = "1"
     let mutable p42SplashEarlyDone = false
     let mutable p42SplashLateDone = false
+    // P74 证据钩子：LV_P74_SHOT=1 时在 60Hz 固定步进下按 splash 帧表拍开场过渡序列，拍完退出。
+    let p74ShotMode = Environment.GetEnvironmentVariable("LV_P74_SHOT") = "1"
+    let p74Frames = [ 8L; 30L; 60L; 100L; 140L ]
+    let mutable p74Saved = Set.empty<int64>
     // P43 证据钩子：LV_P43_SHOT=1 时在真实世界里拍昼/夜两张 HUD 整帧（日历钟卡 + 体力条 + 10 格 hotbar）。
     let p43ShotMode = Environment.GetEnvironmentVariable("LV_P43_SHOT") = "1"
     let mutable p43Step = 0
@@ -2617,6 +2621,20 @@ type LivingVillageGame() as this =
             printfn "p42-shot=done"
             this.Exit()
 
+    /// P74 证据：splash 帧表逐帧落盘（证明开场过渡在变），拍完即退出。
+    member private this.CaptureP74Shot () =
+        if splashActive then
+            match p74Frames |> List.tryFind (fun f -> not (Set.contains f p74Saved) && splashFrame >= f) with
+            | Some frame ->
+                p74Saved <- Set.add frame p74Saved
+                System.IO.Directory.CreateDirectory recordDirectory |> ignore
+                this.SaveBackBuffer(sprintf "%s/p74-splash-%03d.png" recordDirectory frame)
+                printfn "p74-shot=p74-splash-%03d inkStrength=%.3f" frame (InkReveal.inkStrength splashFrame)
+            | None -> ()
+            if p74Saved.Count >= p74Frames.Length then
+                printfn "p74-shot=done"
+                this.Exit()
+
     /// P20 证据：把一次 MapGen 绘制渲染到指定尺寸离屏 target，返回绘制瓦片数与纹理。
     /// P28：可传入世界 tint 与可选 veil tick（夜景取证用）。
     member private this.RenderMapGen (targetWidth: int) (targetHeight: int) (camX: int) (camY: int) (drawFitted: bool) (tint: Color) (veilTick: int64 option) : int * Texture2D =
@@ -2867,6 +2885,8 @@ type LivingVillageGame() as this =
                 this.CaptureMenuShot()
             if p42ShotMode then
                 this.CaptureP42Shot()
+            if p74ShotMode then
+                this.CaptureP74Shot()
             if storyShotMode && storyShotPrepared then
                 storyShotFrame <- storyShotFrame + 1L
                 if not storyShotSaved && storyShotFrame = 20L then
@@ -2990,6 +3010,15 @@ type LivingVillageGame() as this =
             spriteBatch.Draw(pixel, Rectangle(lx - 1, ly - 7, 4, 2), Color(90, 60, 40))
             spriteBatch.Draw(pixel, Rectangle(lx - 2, ly + 5, 6, 2), Color(90, 60, 40))
 
+        // P74 水墨式渐显：柔和墨滴从画布各处晕开、随帧消散，露出后方天色/水面/屋脊。
+        // 单滴 alpha < 255 且用预乘椭圆行落成，绝无实心黑块；绘在标题之下、场景之上。
+        let inkR, inkG, inkB = InkReveal.inkRgb
+        for dab in InkReveal.dabs splashFrame width height do
+            if dab.Alpha > 0 then
+                let inkColor = VillageArt.premultiply inkR inkG inkB dab.Alpha
+                for (runX, runY, runW) in VillageArt.ellipseRuns dab.X dab.Y dab.Rx dab.Ry do
+                    spriteBatch.Draw(pixel, Rectangle(runX, runY, runW, 1), inkColor)
+
         // 标题：淡入 + 上浮，先画深色投影再画亮面。
         let titleRise = int (24.0f * (1.0f - reveal))
         PixelText.draw spriteBatch pixel cjkAtlas (layout.TitleX + 4) (layout.TitleY + titleRise + 4) layout.TitleScale (Color(12, 20, 28, alpha 255)) LaunchScreen.title