fix(siteruntime): M2.12 review nits — observe logger fault + meaningful source fallback (#25)

Replace bare task-discard with ContinueWith(OnlyOnFaulted|ExecuteSynchronously) so a
faulted ISiteEventLogger is logged and swallowed rather than going to the unobserved-task
firehose. Replace the "ScriptRuntimeContext" class-name fallback with the meaningful
"InstanceScript:{instanceName}" identifier (matching the site-event-log source convention).
Update the method doc-comment to state the best-effort contract explicitly. Pin the new
fallback value in the shape-precision test.

src/ZB.MOM.WW.ScadaBridge.SiteRuntime/Scripts/ScriptRuntimeContext.cs

@@ -250,14 +250,38 @@ public class ScriptRuntimeContext
     /// <summary>
     /// M2.12 (#25): fire-and-forget emission of a <c>script</c> Error site event
     /// for a recursion-limit violation. Mirrors the call shape used by
-    /// <c>ScriptExecutionActor</c>'s catch blocks (WP-32 / M1.8). The returned
-    /// task is intentionally discarded by callers (<c>_ =</c>) so the event log
-    /// never blocks or faults the throw that follows. A null logger is a no-op.
+    /// <c>ScriptExecutionActor</c>'s catch blocks (WP-32 / M1.8). A fault from
+    /// the site-event logger is observed-and-dropped (best-effort) via
+    /// <c>ContinueWith(OnlyOnFaulted)</c> — it never blocks or faults the
+    /// <c>_logger.LogError</c> + throw path that follows. A null logger is a no-op.
     /// </summary>
-    private Task EmitRecursionLimitEventAsync(string msg) =>
-        _siteEventLogger?.LogEventAsync(
-            "script", "Error", _instanceName, _sourceScript ?? "ScriptRuntimeContext", msg)
-        ?? Task.CompletedTask;
+    private void EmitRecursionLimitEventAsync(string msg)
+    {
+        if (_siteEventLogger == null)
+            return;
+
+        var source = string.IsNullOrEmpty(_instanceName)
+            ? "recursion-guard"
+            : $"InstanceScript:{_instanceName}";
+
+        var logTask = _siteEventLogger.LogEventAsync("script", "Error", _instanceName, source, msg);
+        if (!logTask.IsCompleted)
+        {
+            logTask.ContinueWith(
+                t => _logger.LogWarning(t.Exception,
+                    "Site event log write failed for recursion-limit violation on instance '{Instance}'",
+                    _instanceName),
+                CancellationToken.None,
+                TaskContinuationOptions.OnlyOnFaulted | TaskContinuationOptions.ExecuteSynchronously,
+                TaskScheduler.Default);
+        }
+        else if (logTask.IsFaulted)
+        {
+            _logger.LogWarning(logTask.Exception,
+                "Site event log write failed for recursion-limit violation on instance '{Instance}'",
+                _instanceName);
+        }
+    }
 
     /// <summary>
     /// Gets the current value of an attribute from the Instance Actor.
@@ -333,7 +357,7 @@ public class ScriptRuntimeContext
                       $"CallScript('{scriptName}') rejected at depth {nextDepth}.";
             _logger.LogError(msg);
             // M2.12 (#25): emit to site event log in addition to ILogger; fire-and-forget.
-            _ = EmitRecursionLimitEventAsync(msg);
+            EmitRecursionLimitEventAsync(msg);
             throw new InvalidOperationException(msg);
         }
 
@@ -498,7 +522,7 @@ public class ScriptRuntimeContext
                 _logger.LogError(msg);
                 // M2.12 (#25): emit to site event log via the parent context's
                 // helper — single emission path, fire-and-forget.
-                _ = _context.EmitRecursionLimitEventAsync(msg);
+                _context.EmitRecursionLimitEventAsync(msg);
                 throw new InvalidOperationException(msg);
             }
 

tests/ZB.MOM.WW.ScadaBridge.SiteRuntime.Tests/Scripts/RecursionLimitSiteEventTests.cs

@@ -143,6 +143,7 @@ public class RecursionLimitSiteEventTests
         string? capturedCategory = null;
         string? capturedSeverity = null;
         string? capturedInstance = null;
+        string? capturedSource = null;
         string? capturedMessage = null;
 
         var loggerMock = new Mock<ISiteEventLogger>();
@@ -157,6 +158,7 @@ public class RecursionLimitSiteEventTests
                     capturedCategory = cat;
                     capturedSeverity = sev;
                     capturedInstance = inst;
+                    capturedSource = src;
                     capturedMessage = msg;
                 })
             .Returns(Task.CompletedTask);
@@ -169,6 +171,8 @@ public class RecursionLimitSiteEventTests
         Assert.Equal("script", capturedCategory);
         Assert.Equal("Error", capturedSeverity);
         Assert.Equal(InstanceName, capturedInstance);
+        // Source fallback: no sourceScript wired, so the helper uses "InstanceScript:{instanceName}".
+        Assert.Equal($"InstanceScript:{InstanceName}", capturedSource);
         Assert.NotNull(capturedMessage);
         Assert.Contains("CallScript", capturedMessage);
         Assert.Contains("2", capturedMessage);   // maxCallDepth in the message