fix(pr-daemon): KillMode=process

Agent tmux sessions the daemon starts live in its cgroup; a restart was
killing every session it had created.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

home/yolo/services.nix

@@ -117,6 +117,9 @@ in
         Environment = [ "PATH=${toolPath}" ];
         Restart = "always";
         RestartSec = 5;
+        # The agent tmux sessions this daemon starts land in its cgroup, so the
+        # default control-group kill takes every running agent down with it.
+        KillMode = "process";
       };
       Install.WantedBy = [ "default.target" ];
     };