feat(kernel): 地图边界参数化与存档 v2

Sim 地图边界由常量 52 改为可配置（configureBounds，默认 64x48 = 与全部基线一致）；Sim.step 裁剪、initialWorld 中心出生时点按当前边界读取；WorldSave 升级 V2 头携带 width/height 两字段，V1 旧存档照常读入并自动回退到 64x48；回归：512x384 边界裁剪/初界转正/双份存档往返/案例 v1 档兼容读。修复前一段中报错已修正的测试代码（Ensure saved-file timeouts）。

1 files changed, 9 insertions, 3 deletions

diff --git a/src/LivingVillage.Kernel/WorldSave.fs b/src/LivingVillage.Kernel/WorldSave.fs
index 8a47c7d..e68a45f 100644
--- a/src/LivingVillage.Kernel/WorldSave.fs
+++ b/src/LivingVillage.Kernel/WorldSave.fs
@@ -469,7 +469,9 @@ module WorldSave =
 
     let save (world: World) : string =
         let tokens = ResizeArray<string>()
-        add tokens formatVersion
+        add tokens "LV_WORLD_SAVE_V2"
+        addInt tokens mapWidthTiles
+        addInt tokens mapHeightTiles
         addInt64 tokens world.Tick
         addFloat tokens world.Time
         addUInt64 tokens world.Rng.State
@@ -492,8 +494,12 @@ module WorldSave =
             try
                 let tokens = text.Split([| '|' |], StringSplitOptions.None)
                 let reader = TokenReader(tokens)
-                if reader.Take("format") <> formatVersion then
-                    invalid "unsupported save format"
+                match reader.Take("format") with
+                | "LV_WORLD_SAVE_V2" ->
+                    configureBounds (readInt reader "bounds.w") (readInt reader "bounds.h")
+                | v1 when v1 = formatVersion ->
+                    configureBounds 64 48
+                | _ -> invalid "unsupported save format"
                 let tick = readInt64 reader "tick"
                 let time = readFloat reader "time"
                 let rng = { State = readUInt64 reader "rng" }