chore: fix venv not correctly resetting PS1

venv

@@ -24,6 +24,7 @@ if [ ! -f "$project_dir/venv" ]; then
     error "please use for \"source venv\" the git root as working directory. I couldn't find \"$project_dir/venv\""
     exit 1
 fi
+export PS1_OLD="${PS1:-}"
 PS1="(OpenCoDE) ${PS1:-}"
 
 info "exporting $(grep -Ece '^[^#=][^#=]*' .env || echo 0) variables from .env"
@@ -64,6 +65,6 @@ function prod-overview() {
 
 info "reload-venv\treload venv file"
 function reload-venv() {
-    PS1="${PS1:23}" # remove "(OpenCoDE) "
+    PS1="${PS1_OLD}" # remove "(OpenCoDE) "
     source "${project_dir:?}/venv"
 }