feat(p40): 石板路连贯带 + 红灯笼入夜光 + LV_P40_SHOT 证据钩子

- VillageArt: cc0PavingTiles 纯函数（路径/门口/桥相连石板格），drawTerrainTile cc0
  分支只铺连贯石板带(19)、孤立散布石板改画草地；fallback/大世界原样
- cc0RedLanternTiles 门口红灯笼(20)，并入 nightLightTilesWith 复用 P14 预乘 alpha 光晕
- Game: LV_P40_SHOT 钩子拍 p40-day/night/boat（PrepareP40Shot/CaptureP40Shot）
- 不写瓦片/不改可达性/不动 Sim.step

2 files changed, 136 insertions, 3 deletions

diff --git a/src/LivingVillage.Desktop/Game.fs b/src/LivingVillage.Desktop/Game.fs
index 7b1dfb1..8c0b8a1 100644
--- a/src/LivingVillage.Desktop/Game.fs
+++ b/src/LivingVillage.Desktop/Game.fs
@@ -295,6 +295,12 @@ type LivingVillageGame() as this =
     let mutable p39Step = 0
     let mutable p39PendingName = ""
     let mutable p39Pending = false
+    // P40 证据钩子：LV_P40_SHOT=1 时在真实 256x192 生成器世界里拍
+    // p40-day / p40-night / p40-boat-closeup（相机贴近乌篷船，便于 2x 特写）。
+    let p40ShotMode = Environment.GetEnvironmentVariable("LV_P40_SHOT") = "1"
+    let mutable p40Step = 0
+    let mutable p40PendingName = ""
+    let mutable p40Pending = false
     let mutable autoplayFrames = 0
     let mutable flowStep = 0
     let mutable flowHold = 0
@@ -691,6 +697,59 @@ type LivingVillageGame() as this =
                 p39PendingName world.Tick world.Avatar.Pos.X world.Avatar.Pos.Y camera.X camera.Y
             p39Step <- p39Step + 1
 
+    /// P40 证据：真实生成器世界里拍昼 / 夜整帧与乌篷船近景。位置取自确定性摆放纯函数，
+    /// 含真实 tint 与 P14 光晕；相机贴近船体便于 2x NEAREST 特写。
+    member private this.PrepareP40Shot () =
+        let placeCameraOn (tileX: int) (tileY: int) =
+            world <- { world with Avatar = { world.Avatar with Pos = { X = float32 (tileX * Sim.tilePixels); Y = float32 (tileY * Sim.tilePixels) } } }
+            this.CenterCamera()
+        let setHour (hour: float) =
+            let tick = M6Presentation.resolveStartTick (Some hour) false
+            world <- { world with Tick = tick; Time = float tick * Sim.dtSeconds }
+        let dayHour = 12.0
+        let nightHour = 23.5
+        if not p40Pending then
+            match riverscapeMap with
+            | None -> this.Exit()
+            | Some map ->
+                let boat =
+                    match VillageArt.cc0BoatTile map with
+                    | Some (bx, by) -> (bx, by)
+                    | None ->
+                        match map.Bridges |> List.sortBy (fun (x, y) -> (x, y)) |> List.tryHead with
+                        | Some (bx, by) -> (bx, by)
+                        | None -> (map.Core.MinX, map.Core.MinY)
+                let boatShot = (fst boat + 1, snd boat)
+                match p40Step with
+                | 0 ->
+                    setHour dayHour
+                    placeCameraOn (fst boat) (snd boat)
+                    p40PendingName <- "p40-day"
+                    p40Pending <- true
+                | 1 ->
+                    setHour nightHour
+                    placeCameraOn (fst boat) (snd boat)
+                    p40PendingName <- "p40-night"
+                    p40Pending <- true
+                | 2 ->
+                    setHour dayHour
+                    placeCameraOn (fst boatShot) (snd boatShot)
+                    p40PendingName <- "p40-boat"
+                    p40Pending <- true
+                | _ ->
+                    printfn "p40-shot=done"
+                    this.Exit()
+
+    /// P40 证据：与 P39 相同，在 `Draw` 末尾落盘当前后台缓冲。
+    member private this.CaptureP40Shot () =
+        if p40Pending then
+            p40Pending <- false
+            System.IO.Directory.CreateDirectory recordDirectory |> ignore
+            this.SaveBackBuffer(sprintf "%s/%s.png" recordDirectory p40PendingName)
+            printfn "p40-shot=%s tick=%d pos=(%.0f,%.0f) camera=(%.0f,%.0f)"
+                p40PendingName world.Tick world.Avatar.Pos.X world.Avatar.Pos.Y camera.X camera.Y
+            p40Step <- p40Step + 1
+
     /// P20 第三步取证：真走位巡游（Sim.step 驱动）沿桥/路/民居门移动，用于桥面行走帧与昼夜录制。
     member private this.RunRiverscapeTour () =
         if not riverscapeTourWatchStarted then
@@ -998,6 +1057,14 @@ type LivingVillageGame() as this =
                     else this.DispatchMenuInput Confirm
                 elif menu.Page = Playing then
                     this.PrepareP39Shot()
+            elif p40ShotMode then
+                if menu.Page = MainMenu then
+                    this.DispatchMenuInput Confirm
+                elif menu.Page = OccupationSelect then
+                    if menu.Selected <> 0 then this.DispatchMenuInput Down
+                    else this.DispatchMenuInput Confirm
+                elif menu.Page = Playing then
+                    this.PrepareP40Shot()
             elif p37ShotMode then
                 this.RunP37Shot()
             elif menu.Page = Playing then
@@ -1379,6 +1446,8 @@ type LivingVillageGame() as this =
                 this.CaptureP36PromptShot()
             if p39ShotMode && menu.Page = Playing then
                 this.CaptureP39Shot()
+            if p40ShotMode && menu.Page = Playing then
+                this.CaptureP40Shot()
 
     /// 启动画面：分层天色 + 屋脊/水面剪影 + 标题淡入上浮 + 跳过提示，全部为帧计数纯函数。
     member private this.DrawSplash() =
diff --git a/src/LivingVillage.Desktop/VillageArt.fs b/src/LivingVillage.Desktop/VillageArt.fs
index e08cde4..0427dea 100644
--- a/src/LivingVillage.Desktop/VillageArt.fs
+++ b/src/LivingVillage.Desktop/VillageArt.fs
@@ -556,7 +556,7 @@ module VillageArt =
     // P34 structure slice: indices into cc0-tiles.png. Kenney Tiny Farm ships no
     // water / roof / wall / railing / door art, so indices 4-11 are self-drawn
     // (provenance in docs/素材来源.md), laid out by this fixed contract.
-    let cc0TileCount = 19
+    let cc0TileCount = 21
     let cc0TileIndexWaterA = 4
     let cc0TileIndexWaterB = 5
     let cc0TileIndexRoofRidge = 6
@@ -574,6 +574,10 @@ module VillageArt =
     let cc0TileIndexStoneLantern = 16
     let cc0TileIndexStall = 17
     let cc0TileIndexReeds = 18
+    // P40 appended elements (indices 19-20). P40 also redrew the boat (14/15) and
+    // sharpened the stone lantern (16); indices 0-13 and 17-18 stay byte-identical.
+    let cc0TileIndexPaving = 19
+    let cc0TileIndexRedLantern = 20
     let cc0WaterFrameCount = 2
     let cc0TileAtlasWidth = Sim.tilePixels * cc0TileCount
     let cc0TileAtlasHeight = Sim.tilePixels
@@ -704,6 +708,47 @@ module VillageArt =
                          && (tileIsWater map x (y - 1) || tileIsWater map x (y + 1)) then
                           yield (x, y) ]
 
+    /// P40 石板路衔接：返回「与通行网络相连」的石板格索引集合。判据为纯几何：
+    /// 该格是石板（code 2），且它本身或四邻属于 `map.Paths`（主路/桥引道/门口）或
+    /// `map.Bridges`（桥面）。稀疏的 `DecorativeStones` 散布石板因远离路网被排除，
+    /// 于是 cc0 模式下石板只沿路径/门口/桥形成连贯带（孤立石板改画草地）。
+    /// 纯函数，只依赖 map（seed 内确定），不写瓦片、不改可达性。
+    let cc0PavingTiles (map: MapGen.Result) : Set<int> =
+        if map.Width <= 0 then
+            Set.empty
+        else
+            let indexOf x y = y * map.Width + x
+            let inMap x y = x >= 0 && x < map.Width && y >= 0 && y < map.Height
+            let isStone x y =
+                inMap x y && map.Tiles.[indexOf x y] = int MapGen.GroundTile.Stone
+            let anchors =
+                (map.Paths @ map.Bridges)
+                |> List.map (fun (x, y) -> indexOf x y)
+                |> Set.ofList
+            let isAnchor x y = inMap x y && Set.contains (indexOf x y) anchors
+            let connected x y =
+                isAnchor x y
+                || isAnchor (x - 1) y
+                || isAnchor (x + 1) y
+                || isAnchor x (y - 1)
+                || isAnchor x (y + 1)
+            [ for y in 0 .. map.Height - 1 do
+                  for x in 0 .. map.Width - 1 do
+                      if isStone x y && connected x y then yield indexOf x y ]
+            |> Set.ofList
+
+    /// P40 红灯笼：在每户民居门口确定性挂一盏红纸灯笼（门口 y，取门格）。
+    /// 与石灯笼形态区分：红纸圆身 + 金穗底座；位置为 (map) 纯函数，同 seed 不变。
+    /// 仅 cc0 模式绘制，且并入 `nightLightTilesWith` 的既有 P14 预乘 alpha 光晕路径。
+    let cc0RedLanternTiles (map: MapGen.Result) : (int * int) list =
+        if map.Width <= 0 then
+            []
+        else
+            (map.Buildings @ map.Farmhouses)
+            |> List.map (fun building -> (building.DoorX, building.DoorY))
+            |> List.filter (fun (x, y) -> x >= 0 && x < map.Width && y >= 0 && y < map.Height)
+            |> List.distinct
+
     /// Ground atlas selection: `Some cc0-tiles.png` when the pack is on, else `None`
     /// so the renderer keeps its procedural Jiangnan ground as the fallback.
     let selectedGroundAtlasRelativePath () : string option =
@@ -883,9 +928,12 @@ module VillageArt =
     /// P30：散落农舍的门窗暖光一并计入。
     /// P39：`includeRoadLanterns` 为真时把主路石灯笼（`cc0LanternTiles`）计入，使夜帧灯笼
     /// 光晕复用同一光晕路径；仅 cc0 模式为真，故 fallback（江南程序图集）不受影响。
+    /// P40：同一开关下把门口红灯笼（`cc0RedLanternTiles`）也计入；红灯笼与石灯笼复用
+    /// 同一条 P14 预乘 alpha 径向光晕路径，不新增光照系统。
     let nightLightTilesWith (includeRoadLanterns: bool) (map: MapGen.Result) : (int * int) list =
         let lanterns = bridgeLanternTiles map
         let roadLanterns = if includeRoadLanterns then cc0LanternTiles map 12 else []
+        let redLanterns = if includeRoadLanterns then cc0RedLanternTiles map else []
         let houseLights =
             (map.Buildings @ map.Farmhouses)
             |> List.collect (fun building ->
@@ -896,7 +944,7 @@ module VillageArt =
                     else
                         [ (building.DoorX, building.DoorY) ]
                 (building.DoorX, building.DoorY) :: windowTiles)
-        lanterns @ roadLanterns @ houseLights |> List.distinct
+        lanterns @ roadLanterns @ redLanterns @ houseLights |> List.distinct
 
     /// 既有夜景灯光源（不含 P39 主路石灯笼），保持既有调用与断言语义不变。
     let nightLightTiles (map: MapGen.Result) : (int * int) list =
@@ -983,13 +1031,26 @@ module VillageArt =
             | Some index -> drawCc0At position index
             | None -> draw position sprite
 
+        // P40 石板路衔接：cc0 模式下只在「与路网/门口/桥相连」的石板格铺连贯石板带，
+        // 稀疏孤立装饰石板改画草地，于是场地上不再出现游离石板。fallback（无 cc0 图集）
+        // 与无 mapGen 的大世界保持原样，故既有输出逐字节不变。
+        let cc0PavingSet =
+            match mapGen, textures.Cc0TileAtlas with
+            | Some map, Some _ -> Some (map.Width, cc0PavingTiles map)
+            | _ -> None
+
         // Procedural terrain for the 512x384 large world: water/pebble/peat codes map
         // onto the jiangnan atlas sprites with deterministic ripple continuity.
         // 生成器世界：1 水 / 2 石板路 / 3 泥炭 / 0 草地。泥炭按草地渲染，路走石板贴图。
         let drawTerrainTile (position: TilePosition) (code: int) =
             match code with
             | 1 -> drawWater position
-            | 2 -> draw position StonePathSprite
+            | 2 ->
+                match cc0PavingSet with
+                | Some (mapWidth, paving) when Set.contains (position.Y * mapWidth + position.X) paving ->
+                    drawCc0At position cc0TileIndexPaving
+                | Some _ -> draw position GrassSprite
+                | None -> draw position StonePathSprite
             // P30 乡村空区：水田（4）走水波动画、菜畦（5）走菜地素材；均为成熟 tile。
             // P34：水田/水网在 CC0 包下同样走自绘 2 相位水面。
             | 4 -> drawWater position
@@ -1053,6 +1114,9 @@ module VillageArt =
                     drawCc0Map stallX stallY cc0TileIndexStall
                 for (reedX, reedY) in cc0ReedTiles map 4 do
                     drawCc0Map reedX reedY cc0TileIndexReeds
+                // P40 红灯笼：门口挂一盏，与主路石灯笼形态区分；夜光晕走同一 P14 路径。
+                for (lanternRedX, lanternRedY) in cc0RedLanternTiles map do
+                    drawCc0Map lanternRedX lanternRedY cc0TileIndexRedLantern
             | None -> ()
         | None -> ()