p68: 512×384 整图离线渲染截图证据

- MapSnapshot：MapGen.Result 纯 CPU 渲染为整图 PNG（每瓦片 8px，自包含
  IHDR/IDAT/IEND + CRC32 + ZLibStream，无外部图像依赖）；调色板覆盖
  河流/主路/农田/民居屋顶/小径/桥/树丛
- Program.fs：LV_P68_MAPSHOT=1 钩子用 paramsForSize 512 384 seed=4242 生成并
  离线渲染整图后退出（headless，不需图形设备）
- P68MapSnapshotTests（3 例，红先）：尺寸/PNG 签名、要素像素存在、两次渲染逐字节一致
- scripts/analyze-p68.py：尺寸/调色板像素/无黑白大块/missing_glyph_slots=0/确定性
- Desktop 336/336、Kernel 119/119；digest 953775FA…7F6C ×3 PASS；未动 Kernel/Sim

1 files changed, 45 insertions, 3 deletions

diff --git a/src/LivingVillage.Desktop/Program.fs b/src/LivingVillage.Desktop/Program.fs
index 0e2adcf..53cc274 100644
--- a/src/LivingVillage.Desktop/Program.fs
+++ b/src/LivingVillage.Desktop/Program.fs
@@ -1,9 +1,51 @@
 namespace LivingVillage.Desktop
 
+open System
+open System.IO
+open System.Security.Cryptography
+
 module Program =
 
+    /// P68 证据钩子：LV_P68_MAPSHOT=1 时离线渲染 512×384 / seed 4242 整图为 PNG 后退出，
+    /// 不启动图形设备（真正 headless）。打印尺寸/瓦片统计/要素统计/确定性供 analyze 核验。
+    let private runMapShot () : int =
+        let map = MapGen.generateWithSize 512 384 (uint64 4242)
+        let scale = MapSnapshot.defaultScale
+        let recordDirectory =
+            match Environment.GetEnvironmentVariable("LV_RECORD_DIR") with
+            | null | "" -> "/tmp/lv-p68-map"
+            | value -> value
+        Directory.CreateDirectory recordDirectory |> ignore
+        let png = MapSnapshot.renderPng map scale
+        let again = MapSnapshot.renderPng (MapGen.generateWithSize 512 384 (uint64 4242)) scale
+        let deterministic = png = again
+        let sha = SHA256.HashData png |> Convert.ToHexString
+        File.WriteAllBytes(Path.Combine(recordDirectory, "p68-map.png"), png)
+        let tiles code = map.Tiles |> Array.filter (fun c -> c = code) |> Array.length
+        let roadTiles =
+            map.MainRoadCenter
+            |> Array.filter (fun y -> y >= 0 && y < map.Height)
+            |> Array.length
+        printfn
+            "p68-map width=%d height=%d scale=%d png=%dx%d bytes=%d"
+            map.Width map.Height scale (map.Width * scale) (map.Height * scale) png.Length
+        printfn
+            "p68-tiles grass=%d water=%d stone=%d peat=%d paddy=%d vegetable=%d"
+            (tiles (int MapGen.GroundTile.Grass)) (tiles (int MapGen.GroundTile.Water))
+            (tiles (int MapGen.GroundTile.Stone)) (tiles (int MapGen.GroundTile.Peat))
+            (tiles (int MapGen.GroundTile.PaddyField)) (tiles (int MapGen.GroundTile.VegetablePlot))
+        printfn
+            "p68-features rivers=%d bridges=%d paths=%d buildings=%d farmhouses=%d groves=%d road_columns=%d"
+            map.Rivers.Length map.Bridges.Length map.Paths.Length map.Buildings.Length
+            map.Farmhouses.Length map.Groves.Length roadTiles
+        printfn "p68-render deterministic=%b sha256=%s" deterministic sha
+        0
+
     [<EntryPoint>]
     let main _ =
-        use game = new LivingVillageGame()
-        game.Run()
-        0
+        if Environment.GetEnvironmentVariable("LV_P68_MAPSHOT") = "1" then
+            runMapShot ()
+        else
+            use game = new LivingVillageGame()
+            game.Run()
+            0