// MacroCtx demo (PoC): shows how ctx (caps) is passed to expand(json, ctx).
// This macro is identity; when caps.env=true it prints a trace line.

static box MacroBoxSpec {
  name() { return "MacroCtxDemo" }

  // json: AST JSON v0 (string)
  // ctx:  JSON string like {"caps":{"io":false,"net":false,"env":false}}
  expand(json, ctx) {
    // Identity demo: do not print to stdout (child output must remain pure JSON)
    // You may inspect ctx (JSON string) and make decisions, but avoid side effects.
    return json
  }
}