feat(desktop): P30 512 民居增密 + 乡村空区填充 + 主路柔化

- MapGen（仅大图尺寸自适应分支，默认 64x48/256x192 不进入、不消费额外 RNG）：
  ① ExtraRiversideHouses 16 -> 30，组团 2-5 座；含基础岸屋的路段优先布组并为每座孤立
     基础民居贴格配对，placeGroup 试排后按「与既有/同组民居足迹间隙 <=2」过滤，孤立单屋不落地。
     512 seed4242：组团民居 24 -> 45，规模 [5;4x6;3x2;2x3]，0 组 <2 座。
  ② 新增 GroundTile.PaddyField=4/VegetablePlot=5（成熟 tile；非水可通行）+ Result.Groves
     （纯视觉）+ Result.Farmhouses（门贴院落路、计入 BFS）；18x14 确定性网格铺田块/树丛/农舍，
     离水 >=3 格、避开路网/核心/民居。草地瓦片 96.3% -> 83.9%，水田 11595 + 菜畦 12877 格。
  ③ Result.MainRoadCenter 逐列中心线，value noise（scale 130、幅度 ±3）确定性缓弯，
     相邻列步长 <=1、遇弯补格保证 4 连通；默认图主街仍笔直。
- VillageArt：水田/菜畦/树丛/农舍渲染（复用成熟 sprite 与同一立面纯函数）、农舍门窗计入夜光、
  新增 drawMapRegion 局部真实离屏渲染。
- Game：P30 证据钩子 LV_MAPGEN_P30_SHOT=1（整图 3072x2304 day/night + 田块/主路 512x256@4px）。
- 回归 +5：组团规模/空区填充/田块合规/农舍可达确定性/主路确定性弯曲。
  Kernel 92 / Desktop 156 全绿；Release 0 警告 0 错误；
  final_digest=953775FAEB2F… 3 次一致、performance_determinism=PASS；
  64x48=6042052、256x192=1284656962 锁定不变。

1 files changed, 126 insertions, 1 deletions

diff --git a/src/LivingVillage.Desktop/Game.fs b/src/LivingVillage.Desktop/Game.fs
index 5f6e99e..3a9a004 100644
--- a/src/LivingVillage.Desktop/Game.fs
+++ b/src/LivingVillage.Desktop/Game.fs
@@ -307,6 +307,8 @@ type LivingVillageGame() as this =
         | v -> match Int32.TryParse v with (true, value) when value > 0 -> value | _ -> 0
     // P28 夜景取证：LV_MAPGEN_NIGHT=1 时整图按 23:30 的真实 tint + 月光 veil 渲染。
     let mapGenNight = Environment.GetEnvironmentVariable("LV_MAPGEN_NIGHT") = "1"
+    // P30 证据钩子：LV_MAPGEN_P30_SHOT=1 时按 P30 规格出图（整图 day/night + 田块局部 + 路网弯曲局部）。
+    let mapGenP30Shot = Environment.GetEnvironmentVariable("LV_MAPGEN_P30_SHOT") = "1"
     let mapGenNightTick = if mapGenNight then M6Presentation.resolveStartTick (Some 23.5) false else 0L
     let mutable mapGenResult = Unchecked.defaultof<MapGen.Result>
     let mutable mapGenGenMs = 0.0
@@ -972,9 +974,132 @@ type LivingVillageGame() as this =
         printfn "mapgen-shot=done"
         this.Exit()
 
+    /// P30 证据：把地图任意 tile 矩形以 cell px/tile 真实离屏渲染，含 tint 与可选 veil/夜光。
+    member private this.RenderMapRegion (tileX0: int) (tileY0: int) (tilesW: int) (tilesH: int) (cell: int) (tint: Color) (veilTick: int64 option) : int * Texture2D =
+        let targetWidth = max 1 (tilesW * cell)
+        let targetHeight = max 1 (tilesH * cell)
+        use target = new RenderTarget2D(this.GraphicsDevice, targetWidth, targetHeight)
+        this.GraphicsDevice.SetRenderTarget target
+        this.GraphicsDevice.Clear(Color(18, 26, 20))
+        spriteBatch.Begin()
+        let glowScale =
+            match veilTick with
+            | Some tick -> (M6Presentation.profileAtTick tick).LanternGlow
+            | None -> 0.0f
+        let drawn =
+            VillageArt.drawMapRegion spriteBatch artTextures pixel tileX0 tileY0 tilesW tilesH cell mapGenResult tint glowScale
+        match veilTick with
+        | Some tick ->
+            let golden = M6Presentation.goldenVeilAlpha tick
+            if golden > 0 then
+                spriteBatch.Draw(pixel, Rectangle(0, 0, targetWidth, targetHeight), VillageArt.premultiply 255 150 70 golden)
+            let moon = M6Presentation.moonlightVeilAlpha tick
+            if moon > 0 then
+                let mr, mg, mb = M6Presentation.moonlightRgb
+                spriteBatch.Draw(pixel, Rectangle(0, 0, targetWidth, targetHeight), VillageArt.premultiply mr mg mb moon)
+        | None -> ()
+        spriteBatch.End()
+        this.GraphicsDevice.SetRenderTarget null
+        let data = Array.zeroCreate<Color> (targetWidth * targetHeight)
+        target.GetData<Color>(data)
+        let texture = new Texture2D(this.GraphicsDevice, targetWidth, targetHeight)
+        texture.SetData(data)
+        (drawn, texture)
+
+    /// P30 田块局部取景：以「窗口内田块最密」的散落农舍为中心（含田块/树丛/院落），
+    /// 优先完整落入画面的农舍；否则退化为首个田块。确定性纯函数。
+    member private this.P30FieldRegion () : int * int =
+        let w = mapGenResult.Width
+        let h = mapGenResult.Height
+        let regionW = 128
+        let regionH = 64
+        let clampX x = max 0 (min (max 0 (w - regionW)) x)
+        let clampY y = max 0 (min (max 0 (h - regionH)) y)
+        let isField code = code = int MapGen.GroundTile.PaddyField || code = int MapGen.GroundTile.VegetablePlot
+        let countFields (cx: int) (cy: int) =
+            let x0 = max 0 (cx - regionW / 2)
+            let x1 = min (w - 1) (cx + regionW / 2)
+            let y0 = max 0 (cy - regionH / 2)
+            let y1 = min (h - 1) (cy + regionH / 2)
+            let mutable n = 0
+            for y in y0 .. y1 do
+                for x in x0 .. x1 do
+                    if isField mapGenResult.Tiles.[y * w + x] then n <- n + 1
+            n
+        let interior =
+            mapGenResult.Farmhouses
+            |> List.filter (fun b -> b.Top >= 16 && b.Top <= h - 80 && b.Left >= regionW / 2 && b.Left <= w - regionW / 2)
+        let candidates = if interior.IsEmpty then mapGenResult.Farmhouses else interior
+        match candidates |> List.sortBy (fun b -> (-(countFields (b.Left + b.Width / 2) (b.Top + 1)), b.Top, b.Left)) |> List.tryHead with
+        | Some b -> (clampX (b.Left + b.Width / 2 - regionW / 2), clampY (b.Top - regionH / 2))
+        | None ->
+            let mutable found = None
+            let mutable y = 0
+            while found.IsNone && y < h do
+                let mutable x = 0
+                while found.IsNone && x < w do
+                    let code = mapGenResult.Tiles.[y * w + x]
+                    if isField code then found <- Some(x, y)
+                    x <- x + 1
+                y <- y + 1
+            match found with
+            | Some (x, y) -> (clampX (x - regionW / 2), clampY (y - regionH / 2))
+            | None -> (clampX (w / 2 - regionW / 2), clampY (h / 2 - regionH / 2))
+
+    /// P30 路网弯曲局部取景：以主路中段某个弯折列为横向中心，纵向对准主路中心线。
+    member private this.P30RoadRegion () : int * int =
+        let w = mapGenResult.Width
+        let h = mapGenResult.Height
+        let regionW = 128
+        let regionH = 64
+        let clampX x = max 0 (min (max 0 (w - regionW)) x)
+        let clampY y = max 0 (min (max 0 (h - regionH)) y)
+        let center = mapGenResult.MainRoadCenter
+        let roadY = if w > 0 then center.[w / 2] else h / 2
+        let bendX =
+            [ for x in 1 .. w - 2 do
+                  if abs (center.[x] - center.[x - 1]) > 0 then yield x ]
+            |> List.tryFind (fun x -> x > w / 4 && x < (3 * w) / 4)
+            |> Option.defaultValue (w / 2)
+        (clampX (bendX - regionW / 2), clampY (roadY - regionH / 2))
+
+    /// P30 证据出图：整图 3072x2304（6px/tile）day/night + 田块局部 512x256（4px/tile）
+    /// + 路网弯曲局部 512x256（4px/tile）。全部真实离屏渲染，拍完即退出。
+    member private this.DrawP30Shot () =
+        System.IO.Directory.CreateDirectory recordDirectory |> ignore
+        let save (name: string) (texture: Texture2D) =
+            use stream = System.IO.File.Create(sprintf "%s/%s.png" recordDirectory name)
+            texture.SaveAsPng(stream, texture.Width, texture.Height)
+        let nightTick = M6Presentation.resolveStartTick (Some 23.5) false
+        let nightTint = (M6Presentation.profileAtTick nightTick).WorldTint
+        let fullW = mapGenResult.Width * 6
+        let fullH = mapGenResult.Height * 6
+        let _, dayTexture = this.RenderMapGen fullW fullH 0 0 true Color.White None
+        use _day = dayTexture
+        save (sprintf "p30-map-%dx%d-seed%d-day" mapGenResult.Width mapGenResult.Height (int mapGenResult.Seed)) dayTexture
+        let _, nightTexture = this.RenderMapGen fullW fullH 0 0 true nightTint (Some nightTick)
+        use _night = nightTexture
+        save (sprintf "p30-map-%dx%d-seed%d-night" mapGenResult.Width mapGenResult.Height (int mapGenResult.Seed)) nightTexture
+        let fx, fy = this.P30FieldRegion ()
+        let _, fieldDay = this.RenderMapRegion fx fy 128 64 4 Color.White None
+        use _fieldDay = fieldDay
+        save "p30-field-cluster-4x-day" fieldDay
+        let _, fieldNight = this.RenderMapRegion fx fy 128 64 4 nightTint (Some nightTick)
+        use _fieldNight = fieldNight
+        save "p30-field-cluster-4x-night" fieldNight
+        let rx, ry = this.P30RoadRegion ()
+        let _, roadDay = this.RenderMapRegion rx ry 128 64 4 Color.White None
+        use _roadDay = roadDay
+        save "p30-roadserp-4x-day" roadDay
+        printfn "p30-shot=done map=%dx%d field_region=(%d,%d) road_region=(%d,%d) night=%b" mapGenResult.Width mapGenResult.Height fx fy rx ry mapGenNight
+        this.Exit()
+
     override this.Draw(gameTime: GameTime) =
         if mapGenShotMode then
-            this.DrawMapGenShot()
+            if mapGenP30Shot then
+                this.DrawP30Shot()
+            else
+                this.DrawMapGenShot()
         else
             if splashActive then
                 this.DrawSplash()