fix: make agent_thread daemon to prevent orphan CLI processes on tab close (#8557)

When a user closes a terminal tab, SIGHUP exits the main thread but
the non-daemon agent_thread kept the entire Python process alive —
stuck in the API call loop with no interrupt signal. Over many
conversations, these orphan processes accumulate and cause massive
swap usage (reported: 77GB on a 32GB M1 Pro).

Changes:
- Make agent_thread daemon=True so the process exits when the main
  thread finishes its cleanup. Under normal operation this changes
  nothing — the main thread already waits on agent_thread.is_alive().
- Interrupt the agent in the finally/exit path so the daemon thread
  stops making API calls promptly rather than being killed mid-flight.

cli.py

@@ -7617,8 +7617,10 @@ class HermesCLI:
                         "error": _summary,
                     }
 
-            # Start agent in background thread
-            agent_thread = threading.Thread(target=run_agent)
+            # Start agent in background thread (daemon so it cannot keep the
+            # process alive when the user closes the terminal tab — SIGHUP
+            # exits the main thread and daemon threads are reaped automatically).
+            agent_thread = threading.Thread(target=run_agent, daemon=True)
             agent_thread.start()
 
             # Monitor the dedicated interrupt queue while the agent runs.
@@ -9626,6 +9628,15 @@ class HermesCLI:
                 raise
         finally:
             self._should_exit = True
+            # Interrupt the agent immediately so its daemon thread stops making
+            # API calls and exits promptly (agent_thread is daemon, so the
+            # process will exit once the main thread finishes, but interrupting
+            # avoids wasted API calls and lets run_conversation clean up).
+            if self.agent and getattr(self, '_agent_running', False):
+                try:
+                    self.agent.interrupt()
+                except Exception:
+                    pass
             # Flush memories before exit (only for substantial conversations)
             if self.agent and self.conversation_history:
                 try: