`module Js : sig ... end`
`module Sys : sig ... end`
`module Error : sig ... end`
`module For_compatibility_only : sig ... end`
`module Typed_array : sig ... end`
`module Int64 : sig ... end`
`module Effect : sig ... end`
`module Promise : sig ... end`

Low-level wrap/unwrap helpers for the `Js_of_ocaml.Promise` binding. Implemented in `runtime/{js,wasm}/promise.{js,wat}`. Wrapping is conditional on the value being thenable, so non-thenable values are passed through unchanged.