org.gamecult.cultlib 2.0.0: the parser's comment and the flush bullet state the exact stamp rule; declare the nil-stamp refusal (Soul s5)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/GameCult.Caching.MessagePack/CultDocumentMessagePackSerialization.cs

@@ -183,8 +183,9 @@ public static class CultDocumentMessagePackSerialization
     }
 
     /// <summary>
-    /// Parses a store snapshot of any format stamp, as every release has. It judges nothing about readability: a store
-    /// reading its own file checks the stamp against the formats it reads, before the body is parsed.
+    /// Parses a store snapshot whose format stamp is a string, of any version. It refuses a nil or binary stamp
+    /// (1.0.61 read a nil stamp as v1). A store reading its own file checks the stamp against the formats it reads,
+    /// before the body is parsed.
     /// </summary>
     public static CultPersistedStoreSnapshot DeserializeSnapshot(byte[] payload) =>
         DeserializeSnapshot(payload, _ => { });

unity/org.gamecult.cultlib/CHANGELOG.md

@@ -106,7 +106,9 @@ All notable changes to this package are documented in this file.
   `cultcache.store.v<N>` with N > 4 (it threw `InvalidOperationException`). A flush
   rewrites any file whose stamp it can read as v1 or v2, or cannot read at all (empty,
   truncated, not a snapshot), which includes a v1 file whose body is corrupt or truncated.
-  It refuses a recognised newer stamp, and it refuses an I/O failure on the read.
+  It refuses any other string stamp, a nil or binary stamp, and an I/O failure on the read.
+  The public `DeserializeSnapshot(byte[])` still parses any string stamp, but refuses a nil
+  or binary stamp (1.0.61 read a nil stamp as v1).
 - `CultMesh.WriteSingleFileDocument` and `WriteSingleFileDocumentPayload` read the
   file they replace, under the store's `<path>.lock`, and refuse (without touching
   it) a file this runtime cannot read, a store stamped with a newer format version,