Parse the free-space fields with a single read

Three echo-through-awk substitutions to split one line into three
variables is what read was made for.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

configs/airootfs/root/configurator

@@ -472,9 +472,7 @@ run_partition_install() {
   fi
 
   local FREE_START_B FREE_END_B FREE_SIZE_B
-  FREE_START_B=$(echo "$FREE_SPACE_INFO" | awk '{print $1}')
+  read -r FREE_START_B FREE_END_B FREE_SIZE_B <<<"$FREE_SPACE_INFO"
-  FREE_END_B=$(echo "$FREE_SPACE_INFO"   | awk '{print $2}')
-  FREE_SIZE_B=$(echo "$FREE_SPACE_INFO"  | awk '{print $3}')
 
   local mib=$((1024 * 1024)) gib=$((1024 * 1024 * 1024))
   local ALIGN=$mib