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_openpilot.sh

@@ -13,6 +13,9 @@ pkill -9 -f 'selfdrive\.' 2>/dev/null
 pkill -9 -f 'system\.' 2>/dev/null
 pkill -9 -f './ui' 2>/dev/null
 pkill -9 -f 'selfdrive/ui/text' 2>/dev/null
+# `text` is a shell wrapper that execs `./_text` — after exec the running
+# process's argv has no path, so kill by exact comm too.
+pkill -9 -x _text 2>/dev/null
 sleep 1
 
 # CLEARPILOT: ensure params persistence dir is owned by comma:comma. Editing