cue: Value needs a method to finalize a value

[myitcv]

Is your feature request related to a problem? Please describe.

Consider the following code:

-- go.mod --
module mod.example

go 1.22.3

require cuelang.org/go v0.9.2

-- main.go --
package main

import (
	"fmt"

	"cuelang.org/go/cue/cuecontext"
)

func main() {
	ctx := cuecontext.New()
	v := ctx.CompileString(`{a:"a"} | {a:"a",b!:string}`)
	fmt.Printf("%v\n", v)
}

As expected this gives:

{
        a: "a"
} | {
        a:  "a"
        b!: string
}

i.e. v is incomplete.

What I would like is a method on cue.Value that allows me to finalise v to give a cue.Value which would render as:

{
        a: "a"
}

Noting that at the time of writing #3285 is a bug. But even if that bug were fixed, there is no method on cue.Value that I can call with cue.Final to say "there is nothing more to come".

Describe the solution you'd like

A method on cue.Value that accepts cue.Final() and returns a finalised cue.Value.

Describe alternatives you've considered

Nothing particularly elegant, other than going to and from CUE source.

Additional context

n/a