Sandboxed code evaluation with AST-level safety checks.

Evaluates Elixir code strings in a spawned process with:

• AST validation — before evaluation, the code is parsed and walked to reject dangerous forms (defmodule, import, spawn, send, receive, etc.) and calls to modules not in the allow-list.
• Module allow-list — only built-in safe modules (Kernel, Enum, Map, String, …) and explicitly passed modules may be called. If only some functions from a module should be exposed, wrap them in a dedicated facade module.
• Timeout — evaluation runs in a monitored process that is killed if it exceeds the deadline.

Examples

iex> {:ok, {4, _}} = Legion.Sandbox.execute("2 + 2", 5_000)

iex> {:ok, {6, _}} = Legion.Sandbox.execute("Enum.sum([1, 2, 3])", 5_000)

iex> {:error, msg} = Legion.Sandbox.execute("System.halt()", 5_000)
iex> msg =~ "Module System is not allowed"
true

iex> {:error, msg} = Legion.Sandbox.execute("import Enum", 5_000)
iex> msg =~ "import is not allowed"
true