fix(frontend): Filter out started events when session is completed

The Activity Timeline was showing both "Session Started" (with spinning icon)
and "Session Completed" events for the same session, making it appear that
sessions were still running even after completion.

Now filters out session_started events when a corresponding session_completed
or session_failed event exists for the same sessionId.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>
Signed-off-by: sallyom <[email protected]>

Author: sallyom

components/frontend/src/components/workspaces/bugfix/BugTimeline.tsx

@@ -40,8 +40,25 @@ interface BugTimelineProps {
 
 // eslint-disable-next-line @typescript-eslint/no-unused-vars
 export default function BugTimeline({ workflowId, events, sessions = [], className }: BugTimelineProps) {
+  // Filter out session_started events if there's a corresponding completed/failed event
+  const filteredEvents = events.filter((event) => {
+    // Keep all non-started events
+    if (event.type !== 'session_started') {
+      return true;
+    }
+
+    // For session_started events, only keep if there's no corresponding completed/failed event
+    const hasCompletionEvent = events.some(
+      (e) =>
+        e.sessionId === event.sessionId &&
+        (e.type === 'session_completed' || e.type === 'session_failed')
+    );
+
+    return !hasCompletionEvent;
+  });
+
   // Sort events by timestamp (newest first)
-  const sortedEvents = [...events].sort((a, b) =>
+  const sortedEvents = [...filteredEvents].sort((a, b) =>
     new Date(b.timestamp).getTime() - new Date(a.timestamp).getTime()
   );