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.

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