Appending | to each line and a last line . is a jq program that reproduces the original json.

  jq -r '
   ( tostream
     | select(length > 1)
     | (
       .[0] | map(
         if type == "number"
         then "[" + tostring + "]"
         else "." + .
         end
       ) | join("")
     )
     + " = "
     + (.[1] | @json)
     + " |"
   ),
   "."
  '