refactor: drop eval from pick_live_party

Select the chosen positional argument with shift + "$1" instead of
building a $pick-indexed variable reference through eval.

party

@@ -668,7 +668,8 @@ pick_live_party() {
     if [ "$pick" -lt 1 ] || [ "$pick" -gt $# ]; then
         echo "party: out of range" >&2; return 1
     fi
-    eval "roster_read \"\$$pick\""
+    shift $((pick - 1))
+    roster_read "$1"
 }
 
 # Resolve the party a join or knock targets: the named party if given,