feat(art): 生成器民居改用黛瓦/木墙/门窗部件 + 村民可见性日志钩子（P24）

- drawMapStructures 用 RoofRidge/RoofEave + WallWood/WallWindow + Door 精灵替换原矩形色块。
- LV_NPC_VISIBLE_LOG=1 每秒打印 visible-npcs=K of 30，作为大世界村民渲染证据。

2 files changed, 28 insertions, 7 deletions

diff --git a/src/LivingVillage.Desktop/Game.fs b/src/LivingVillage.Desktop/Game.fs
index 8309867..bcc4094 100644
--- a/src/LivingVillage.Desktop/Game.fs
+++ b/src/LivingVillage.Desktop/Game.fs
@@ -215,6 +215,8 @@ type LivingVillageGame() as this =
     let mutable avatarMoving = false
     let unlockFps = Environment.GetEnvironmentVariable("LV_UNLOCK_FPS") = "1"
     let perfSummaryMode = Environment.GetEnvironmentVariable("LV_PERF_SUMMARY") = "1"
+    // P24 证据钩子：每秒打印屏幕内可见 NPC 数，证明大世界村民确实被渲染。
+    let npcVisibleLog = Environment.GetEnvironmentVariable("LV_NPC_VISIBLE_LOG") = "1"
     let mutable fpsSamples: float list = []
     let mutable fpsFrames = 0
     let mutable fpsSeconds = 0.0
@@ -751,6 +753,18 @@ type LivingVillageGame() as this =
             if perfSummaryMode then
                 fpsSamples <- fps :: fpsSamples
             printfn $"fps={fps:F1} tick={world.Tick} pos=({world.Avatar.Pos.X:F0},{world.Avatar.Pos.Y:F0})"
+            if npcVisibleLog then
+                let viewport = this.GraphicsDevice.Viewport
+                let margin = float32 Sim.tilePixels
+                let visible =
+                    world.Npcs
+                    |> Array.filter (fun npc ->
+                        let sx = npc.Pos.X - camera.X
+                        let sy = npc.Pos.Y - camera.Y
+                        sx >= -margin && sx <= float32 viewport.Width + margin
+                        && sy >= -margin && sy <= float32 viewport.Height + margin)
+                    |> Array.length
+                printfn $"visible-npcs={visible} of {world.Npcs.Length}"
         prevKb <- kb
 
     override this.EndRun() =
diff --git a/src/LivingVillage.Desktop/VillageArt.fs b/src/LivingVillage.Desktop/VillageArt.fs
index 3ad5b19..12c17ba 100644
--- a/src/LivingVillage.Desktop/VillageArt.fs
+++ b/src/LivingVillage.Desktop/VillageArt.fs
@@ -616,13 +616,20 @@ module VillageArt =
         for (x, y) in map.Bridges do
             spriteBatch.Draw(textures.TileAtlas, XnaRectangle(tileX x, tileY y, cell, cell), bridgeSource, XnaColor.White)
         for building in map.Buildings do
-            for row in building.Top .. building.Top + building.Height - 1 do
-                // 白墙朝向道路一行（门所在行），其余为黑瓦屋顶，两侧河岸朝向一致。
-                let color =
-                    if row = building.DoorY then XnaColor(236, 232, 220)
-                    else XnaColor(48, 52, 60)
-                fillRect spriteBatch pixel color (tileX building.Left) (tileY row) (building.Width * cell) (cell)
-            fillRect spriteBatch pixel (XnaColor(96, 60, 42)) (tileX building.DoorX) (tileY building.DoorY) cell cell
+            let left = building.Left
+            let right = building.Left + building.Width - 1
+            // P24：改用 256x192 同款民宅部件——黛瓦（脊/檐）+ 木墙/窗 + 门。
+            for row in building.Top .. building.DoorY - 1 do
+                let roofSprite = if row = building.Top then RoofRidgeSprite else RoofEaveSprite
+                let source = tileSourceRectangle roofSprite
+                for x in left .. right do
+                    spriteBatch.Draw(textures.TileAtlas, XnaRectangle(tileX x, tileY row, cell, cell), source, XnaColor.White)
+            for x in left .. right do
+                let wallSprite =
+                    if x = building.DoorX then DoorSprite
+                    elif (x - left) % 2 = 0 then WallWindowSprite
+                    else WallWoodSprite
+                spriteBatch.Draw(textures.TileAtlas, XnaRectangle(tileX x, tileY building.DoorY, cell, cell), tileSourceRectangle wallSprite, XnaColor.White)
 
     /// 桥头灯笼瓦片：每座桥每列的最上/最下一格（桥两端），用于挂灯笼与夜间暖光。
     let bridgeLanternTiles (map: MapGen.Result) : (int * int) list =