Fix dangling activity exception for multi-trigger flowcharts

Modified MaybeScheduleOutboundActivitiesAsync to handle activities that appear
dangling from one trigger's perspective but were legitimately scheduled by another
trigger. Now only throws exception if activity has no outbound connections.

Co-authored-by: sfmskywalker <938393+sfmskywalker@users.noreply.github.com>

Author: Copilot

src/modules/Elsa.Workflows.Core/Activities/Flowchart/Activities/Flowchart.Counters.cs

@@ -171,10 +171,16 @@ private static async ValueTask<bool> MaybeScheduleOutboundActivitiesAsync(FlowGr
     {
         bool hasScheduledActivity = false;
 
+        // Get the outbound connections for this activity
+        var outboundConnections = flowGraph.GetOutboundConnections(activity);
+        
         // Check if the activity is dangling (i.e., it is not reachable from the flowchart graph)
-        if (flowGraph.IsDanglingActivity(activity))
+        // Only throw an exception if the activity is truly dangling (has no outbound connections)
+        // In multi-trigger scenarios, an activity may appear dangling from one trigger's perspective
+        // but was legitimately scheduled by another trigger
+        if (flowGraph.IsDanglingActivity(activity) && outboundConnections.Count == 0)
         {
-            throw new($"Activity {activity.Id} is not reachable from the flowchart graph. Unable to schedule it's outbound activities.");
+            throw new($"Activity {activity.Id} is not reachable from the flowchart graph and has no outbound connections. Unable to schedule it's outbound activities.");
         }
 
         // Register the activity as visited unless it was executed due to a backward connection
@@ -184,7 +190,7 @@ private static async ValueTask<bool> MaybeScheduleOutboundActivitiesAsync(FlowGr
         }
 
         // Process each outbound connection from the current activity
-        foreach (var outboundConnection in flowGraph.GetOutboundConnections(activity))
+        foreach (var outboundConnection in outboundConnections)
         {
             var connectionFollowed = outcomes.Names.Contains(outboundConnection.Source.Port);
             flowScope.RegisterConnectionVisit(outboundConnection, connectionFollowed);