kill stale text-error window by comm too, not just path

selfdrive/ui/text is a shell wrapper that execs ./_text. After exec,
the running process's argv has no path component, so
pkill -f 'selfdrive/ui/text' silently misses it. Add pkill -x _text
alongside the existing path-pattern kills in build_only.sh,
launch_openpilot.sh, and launch_chffrplus.sh.

launch_chffrplus.sh

@@ -79,8 +79,11 @@ function launch {
     agnos_init
   fi
 
-  # CLEARPILOT: kill stale error display from previous build/run
+  # CLEARPILOT: kill stale error display from previous build/run.
+  # `text` is a wrapper that execs ./_text — running process is named _text
+  # with no path, so kill by exact comm too.
   pkill -f "selfdrive/ui/text" 2>/dev/null
+  pkill -x _text 2>/dev/null
 
   # write tmux scrollback to a file
   tmux capture-pane -pq -S-1000 > /tmp/launch_log