docs(scripting): ctx.CancellationToken also fires on caller cancellation

Review m-6. The XML doc said the token is cancelled on timeout only.
ScriptRunGuard links it to the caller's token
(CreateLinkedTokenSource(ct)), so it is also cancelled on shutdown or
when the evaluating actor stops mid-run. The doc now says so.

Refs #731 #734
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT

src/Core/ZB.MOM.WW.OtOpcUa.Core.Scripting.Abstractions/ScriptContext.cs

@@ -82,7 +82,8 @@ public abstract class ScriptContext
 
     /// <summary>
     ///     The current run's cancellation token. The run guard cancels it when the run exceeds its wall-clock
-    ///     budget, so a long-running script can poll <c>ctx.CancellationToken.IsCancellationRequested</c> (or call
+    ///     budget, and it is linked to the caller's token, so it is also cancelled when the caller cancels (host
+    ///     shutdown, an actor stopping mid-run). A long-running script can poll <c>ctx.CancellationToken.IsCancellationRequested</c> (or call
     ///     <c>ThrowIfCancellationRequested()</c>) and end its own abandoned run instead of holding a pool thread
     ///     until it returns. Cooperative only: a script that never looks at it still runs to completion as an
     ///     orphan. <see cref="CancellationToken.None"/> outside a run.