docs(siteruntime): compile gate is synchronous by design; Expression alarms share the bounded script pool (plan R2-03 T7)

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Deployment/DeployCompileValidator.cs

@@ -14,8 +14,11 @@ namespace ZB.MOM.WW.ScadaBridge.SiteRuntime.Deployment;
 /// deployment; no partial state is applied).
 ///
 /// Because it holds no actor state and only calls the (stateless)
-/// <see cref="ScriptCompilationService"/>, it is safe to run off the singleton
-/// mailbox on a <c>Task.Run</c> thread — the deploy path never blocks on Roslyn.
+/// <see cref="ScriptCompilationService"/>, it is pure and thread-safe; the Deployment
+/// Manager nevertheless invokes it <em>synchronously on the singleton's actor thread</em>
+/// as a pure prefix step, preserving mailbox-FIFO deploy ordering (see
+/// <see cref="Actors.DeploymentManagerActor.HandleDeploy"/>). Compiles of unchanged
+/// script bodies are deduped by the process-wide compile cache.
 /// </summary>
 public sealed class DeployCompileValidator
 {