`<~` doesn't preserve the data type of `$ENV.PATH`

[lmorg]

Describe the bug:

$ENV.PATH <~ %[ foobar ]

should append :foobar to $PATH. Instead it converts $PATH to JSON and adds it as the first array element (escaped as string) inside another JSON array with foobar as the second array element.

Behaviour works as expected for local variables, even of paths type.