Builds nested Spark.Options schemas from flat parameter definitions.

This module converts the flat [{path, opts}] format from __bb_parameter_schema__/0 into nested keyword lists suitable for validating start_link options.

Example

iex> flat = [
...>   {[:motion, :max_speed], [type: :float, default: 1.0]},
...>   {[:motion, :acceleration], [type: :float, default: 0.5]},
...>   {[:debug_mode], [type: :boolean, default: false]}
...> ]
iex> BB.Parameter.Schema.build_nested_schema(flat)
[
  debug_mode: [type: :boolean],
  motion: [type: :keyword_list, keys: [
    acceleration: [type: :float],
    max_speed: [type: :float]
  ]]
]