fix: bug when cancelling tasks, tool call message subkind

backend/src/agent.py

@@ -148,7 +148,7 @@ class Agent:
                 thread_id=message.thread_id,
                 content=stream,
                 kind="log",
-                subkind="reasoning",
+                subkind="tool-call",
             )
             run.emit_event('chat-message', {
                 'messageId': new_message['id'],
@@ -220,7 +220,10 @@ class AgentRun:
         self.reasoning = None
         
         # Cancellation tracking
+        # You should use 'cancelled', task and thread are for
+        # external tasks that cannot be cancelled reliably
         self.task = None  # For asyncio tasks
+        self.thread = None
         self.cancelled = False
 
         app.tmp.runs[self.id] = self