fix(flow-debugger): final-review remediation — 2000-row trace pull, shared ExceptionHeader parser, surrogate-safe clip, wording, alarm source, register renumber (I1/I2/M1-M8)

src/ZB.MOM.WW.ScadaBridge.InboundAPI/InboundScriptLogger.cs

@@ -209,11 +209,20 @@ public sealed class InboundScriptLogger
         }
     }
 
+    /// <summary>
+    /// Applies the per-message cap, marking a truncated message with a trailing ellipsis.
+    ///
+    /// <para>Final review M2 — mirrors the site runtime's <c>ScriptLogger.Clip</c>: cuts one char
+    /// short when the cap would land between the two halves of a surrogate pair, so an emoji
+    /// straddling the boundary is dropped whole rather than leaving a lone surrogate that breaks
+    /// JSON serialization downstream.</para>
+    /// </summary>
     private static string Truncate(string? message)
     {
         if (string.IsNullOrEmpty(message)) return string.Empty;
-        return message.Length <= MaxMessageChars
-            ? message
-            : string.Concat(message.AsSpan(0, MaxMessageChars), "…");
+        if (message.Length <= MaxMessageChars) return message;
+
+        var keep = char.IsHighSurrogate(message[MaxMessageChars - 1]) ? MaxMessageChars - 1 : MaxMessageChars;
+        return string.Concat(message.AsSpan(0, keep), "…");
     }
 }