e1608: do not fight a hardware trigger, stop the scan on a failed connect, daemon drop timer in the mock

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tools/mock_e1608.py

@@ -327,7 +327,9 @@ class Board:
                 self.first_conn = time.monotonic()
         close_quietly(old)
         if first and self.args.drop_after > 0:
-            threading.Timer(self.args.drop_after, self.drop).start()
+            timer = threading.Timer(self.args.drop_after, self.drop)
+            timer.daemon = True
+            timer.start()
         try:
             while True:
                 b = conn.recv(1)