kpt: kpt/kyaml doesn't parse yaml sequence nodes correctly

The following is expected workflow

@seh So summarizing your request…

If you start with

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
patches:
- target:
    kind: Something
  patch: |-
    - op: add
      path: placeholder
      value: known

and do

kpt cfg create-setter . some-json-pointer placeholder

The output should be

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
patches:
- target:
    kind: Something
  patch: |-
    - op: add
      path: placeholder # {"$kpt-set":"some-json-pointer"}
      value: known

and later on

kpt cfg set . some-json-pointer new-placeholder

should give output

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
patches:
- target:
    kind: Something
  patch: |-
    - op: add
      path: new-placeholder # {"$kpt-set":"some-json-pointer"}
      value: known

But it doesn’t work as expected. Investigate and fix it.