perf(deployment): staleness/comparison paths no longer Roslyn-compile every script — deploy gate remains the authoritative compile

Claude-Session: https://claude.ai/code/session_01MtdgwpEeCUn6cUA5f1LMPj

src/ZB.MOM.WW.ScadaBridge.TemplateEngine/Validation/ValidationService.cs

@@ -95,6 +95,14 @@ public class ValidationService
     /// <c>$ref</c> are unaffected (behavior unchanged), and a <c>$ref</c> with no
     /// resolver is treated as dangling (the safe option).
     /// </param>
+    /// <param name="validateScriptCompilation">
+    /// <c>true</c> (default) runs the authoritative Roslyn <see cref="ValidateScriptCompilation"/>
+    /// stage — the single most expensive check (a non-collectible assembly load per script).
+    /// <c>false</c> skips ONLY that stage; every other structural/semantic check still runs.
+    /// Read-only staleness/comparison callers (DeploymentManager's FlatteningPipeline on its
+    /// comparison/probe paths) pass <c>false</c> because they need only the flattened config and
+    /// revision hash, not a compile. The deploy gate keeps the default (<c>true</c>).
+    /// </param>
     /// <returns>A merged <see cref="ValidationResult"/> aggregating all pipeline stage outcomes.</returns>
     public ValidationResult Validate(
         FlattenedConfiguration configuration,
@@ -102,7 +110,8 @@ public class ValidationService
         IReadOnlySet<string>? alarmCapableConnectionNames = null,
         bool enforceConnectionBindings = false,
         IReadOnlySet<string>? siteConnectionNames = null,
-        Func<string, string?>? resolveSchemaRef = null)
+        Func<string, string?>? resolveSchemaRef = null,
+        bool validateScriptCompilation = true)
     {
         ArgumentNullException.ThrowIfNull(configuration);
 
@@ -110,7 +119,13 @@ public class ValidationService
         {
             ValidateFlatteningSuccess(configuration),
             ValidateNamingCollisions(configuration),
-            ValidateScriptCompilation(configuration),
+            // The Roslyn compile is the single most expensive validation stage (a
+            // non-collectible InteractiveAssemblyLoader assembly load per script).
+            // Read-only staleness/comparison callers pass validateScriptCompilation:
+            // false to skip ONLY this stage; every other structural/semantic check
+            // still runs. The deploy gate keeps the default (true) — it is the
+            // authoritative compile.
+            validateScriptCompilation ? ValidateScriptCompilation(configuration) : ValidationResult.Success(),
             ValidateAlarmTriggerReferences(configuration),
             ValidateScriptTriggerReferences(configuration),
             ValidateExpressionTriggers(configuration),