If I am using cast_embed/3, how do I clear an embeds_many entry?

I have a table flows that has a options JSONB column

CREATE TABLE flows (
  id bigint generated always as identity primary key,
  options JSONB
);

I have defined the schema as follows:

defmodule Test.Flow do
  use Ecto.Schema
  import Ecto.Changeset

  defmodule Option do
    use Ecto.Schema
    import Ecto.Changeset

    @primary_key false
    embedded_schema do
      field :value, :string
    end

    def changeset(opts \\ %__MODULE__{}, attrs) do
      cast(opts, attrs, [:value])
    end
  end

  schema "flows" do
    embeds_many :options, Option, on_replace: :delete
  end

  def changeset(flows \\ %__MODULE__{}, attrs) do
    flows
    |> cast(attrs, [:id])
    |> cast_embed(:options)
    |> validate_length(:options, min: 1)
  end
end

In Typescript type terms, the type would look something like this:

interface Flow {
  id: number
  options?: [Option, ...Option[]] | null
}

interface Option {
  value: string
}

That is, options should be null or an array of at least one Option. But I can’t make that happen:

iex(1)> {:ok, f} = Repo.insert(Test.Flow.changeset(%{})
{:ok,
 %Test.Flow{
   __meta__: #Ecto.Schema.Metadata<:loaded, "flows">,
   id: 1,
   options: []
 }}
iex(2)> Test.Flow.changeset(f, %{options: nil})
#Ecto.Changeset<
  action: nil,
  changes: %{},
  errors: [options: {"is invalid", [validation: :embed, type: {:array, :map}]}],
  data: #Test.Flow<>,
  valid?: false
>
iex(3)> Repo.update!(f, %{options: [%{}]})
%Test.Flow{
  __meta__: #Ecto.Schema.Metadata<:loaded, "flows">,
  id: 1,
  options: [%Test.Flow.Option{value: nil}]
}
iex(4)> f = Repo.get(TestFlow, 1)
%Test.Flow{
  __meta__: #Ecto.Schema.Metadata<:loaded, "flows">,
  id: 1,
  options: [%Test.Flow.Option{value: nil}]
}
iex(5)> Test.Flow.changeset(f, %{options: []})
#Ecto.Changeset<
  action: nil,
  changes: %{
    options: [
      #Ecto.Changeset<action: :replace, changes: %{}, errors: [],
       data: #Test.Flow.Option<>, valid?: true>
    ]
  },
  errors: [
    options: {"should have at least %{count} item(s)",
     [count: 1, validation: :length, kind: :min, type: :list]}
  ],
  data: #Test.Flow<>,
  valid?: false
>

This feels like it should be possible, if not easy, but I don’t really see a way to do it, especially since there doesn’t appear to be a distinction between attrs of %{} (options is missing) and %{options: nil} (options is explicitly nulled). That is, when I do Test.Flow.changeset(f, %{options: nil}).changes, I get %{}.

I suppose that I could use a sigil value (:none), but that feels…awkward.