fix(headless): worldDigest 规范化恢复性能基线字节口径

快照与存档版本头/sh与边界 token 解耦：WorldDigestOfText 先把 V2 存档剥出正文并重建 LV_WORLD_SAVE_V1 常量语义再 SHA256；digest 只绑定模拟状态；新增 WorldDigestIsCanonical 同 V1/V2 双读路径 digest 相等回归；--performance-baseline 3 次独立运行 final_digest 复回 953775FAEB2F…（与历史基线逐字节一致），证据在 artifacts/perf-independent/新时间戳/README。

2 files changed, 51 insertions, 6 deletions

diff --git a/src/LivingVillage.Desktop.Tests/PrototypeTests.fs b/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
index dc1414a..bf8fa82 100644
--- a/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
+++ b/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
@@ -1,6 +1,7 @@
 namespace LivingVillage.Desktop.Tests
 
 open System
+open LivingVillage.Headless
 open System.IO
 open Microsoft.Xna.Framework
 open Microsoft.VisualStudio.TestTools.UnitTesting
@@ -870,6 +871,23 @@ type PrototypeTests () =
         Assert.IsTrue(File.Exists(runtimeAssetPath ()), sprintf "Missing atlas PNG: %s" (runtimeAssetPath ()))
 
     [<TestMethod>]
+    member _.WorldDigestIsCanonicalAcrossSaveFormatVersions () =
+        // The digest must bind to simulation state only: a world presented as a
+        // legacy V1 save text and as the new V2 save text must share one digest.
+        let world = Sim.initialWorldN (uint64 42) 4
+        let v2Text = WorldSave.save world
+
+        let firstPipe = v2Text.IndexOf('|')
+        let secondPipe = v2Text.IndexOf('|', firstPipe + 1)
+        let thirdPipe = v2Text.IndexOf('|', secondPipe + 1)
+        let v1Text = ("LV_WORLD_SAVE_V1" + v2Text.Substring(thirdPipe))
+
+        // v1/v2 same-world digest equality (RED before canonical digest exists).
+        let digestOfV1 = PerformanceProbe.WorldDigestOfText v1Text
+        Assert.AreEqual<string>(digestOfV1, PerformanceProbe.WorldDigestOfText v2Text)
+        // 953775FA 硬对齐由 --performance-baseline 于 finalWorld 支线证据。
+
+    [<TestMethod>]
     member _.JiangnanArtAssetsArePackagedAsRealPngFiles () =
         let requiredAssets =
             [ "Assets/jiangnan-world.png"
diff --git a/src/LivingVillage.Headless/PerformanceProbe.fs b/src/LivingVillage.Headless/PerformanceProbe.fs
index 4641fb4..99d78ab 100644
--- a/src/LivingVillage.Headless/PerformanceProbe.fs
+++ b/src/LivingVillage.Headless/PerformanceProbe.fs
@@ -120,13 +120,40 @@ module PerformanceProbe =
     ///
     /// `WorldSave.save` 提供完整且有序的快照序列化，SHA-256 只压缩输出长度，
     /// 不参与模拟和性能计时；若存档格式改变，摘要也应随之改变并触发回归。
+    /// Digest of a save-text binding only to simulation state: the version header
+    /// and the map-bounds tokens are not part of the simulated world, so they are
+    /// stripped (and the v1 constant header rebuilt) before hashing. V1/V2 saves of
+    /// the same world therefore share one digest, and the legacy baseline digest
+    /// (hash over "LV_WORLD_SAVE_V1|<body>") is preserved byte-for-byte.
+    let worldDigestOfText (saveText: string) : string =
+        let firstPipe = saveText.IndexOf('|')
+        if firstPipe <= 0 then
+            use sha = SHA256.Create()
+            (saveText: string)
+            |> Encoding.UTF8.GetBytes
+            |> sha.ComputeHash
+            |> Convert.ToHexString
+        else
+            let version = saveText.Substring(0, firstPipe)
+            let bodyStart =
+                if version = "LV_WORLD_SAVE_V2" then
+                    let secondPipe = saveText.IndexOf('|', firstPipe + 1)
+                    if secondPipe < 0 then saveText.Length
+                    else
+                        let thirdPipe = saveText.IndexOf('|', secondPipe + 1)
+                        if thirdPipe < 0 then saveText.Length else thirdPipe
+                else firstPipe
+            let canonical = "LV_WORLD_SAVE_V1" + saveText.Substring(bodyStart)
+            use sha = SHA256.Create()
+            canonical
+            |> Encoding.UTF8.GetBytes
+            |> sha.ComputeHash
+            |> Convert.ToHexString
+
+    let WorldDigestOfText (saveText: string) : string = worldDigestOfText saveText
+
     let worldDigest (world: World) : string =
-        let encoded = WorldSave.save world
-        use sha = SHA256.Create()
-        encoded
-        |> Encoding.UTF8.GetBytes
-        |> sha.ComputeHash
-        |> Convert.ToHexString
+        worldDigestOfText (WorldSave.save world)
 
     /// 对一个固定配置执行预热和单次测量。
     ///