harden(vtag): exclude backslash from passthrough capture + parity tests (A review)

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

@@ -7,10 +7,17 @@ using System.Text.RegularExpressions;
 /// which can be evaluated by returning the dependency value directly — no Roslyn compilation.
 /// Narrow, exact pattern: any near-miss returns false and falls through to the Roslyn path.
 /// </summary>
+/// <remarks>
+/// Physically defined in the Core.Scripting.Abstractions assembly (Roslyn-free, so ControlPlane
+/// can reference it); the namespace is Core.Scripting to keep consumer using-directives unchanged.
+/// </remarks>
 public static partial class PassthroughScript
 {
     // ^ \s* return \s+ ctx . GetTag ( "X" ) . Value ; \s* $  (whitespace-tolerant around tokens)
-    [GeneratedRegex(@"^\s*return\s+ctx\s*\.\s*GetTag\s*\(\s*""([^""]+)""\s*\)\s*\.\s*Value\s*;\s*$")]
+    // Tag-name class [^"\\] excludes both the closing quote and backslash: a literal containing a
+    // backslash escape (e.g. "a\\b" → runtime name a\b) won't match, so it correctly falls through
+    // to Roslyn, which interprets the escape and resolves the actual dependency key.
+    [GeneratedRegex(@"^\s*return\s+ctx\s*\.\s*GetTag\s*\(\s*""([^""\\]+)""\s*\)\s*\.\s*Value\s*;\s*$")]
     private static partial Regex MirrorRegex();
 
     /// <summary>True if <paramref name="source"/> is the mirror passthrough shape; outputs the referenced tag.</summary>