fix(plugins): close LA5 ownership races

src/AcDream.Launcher.Core/Launching/SessionConfigDocument.cs

@@ -98,8 +98,10 @@ public sealed class SessionDescriptor
 
     public SessionCredentialDescriptor Credential { get; init; } = new();
 
-    /// <summary>Omitted (never an empty array) when the character has no
-    /// configured plugin set.</summary>
+    /// <summary>Plugin allow-list. Omitted or JSON <c>null</c> means load all
+    /// discovered plugins (the developer flow); an explicit empty array means
+    /// load none. Launcher-composed normal-empty and probe sessions therefore
+    /// emit <c>[]</c>.</summary>
     public List<string>? Plugins { get; init; }
 
     /// <summary>Omitted (never an empty array) when the character has no