// ============================================================================
// Helper Functions
// ============================================================================
/// `SiLU` (Swish) activation: x * sigmoid(x)
///
/// ONE PATH: Delegates to `nn::functional::silu` (canonical implementation).
/// UCBD ยง4: There is ONE way to compute SiLU in aprender.
/// Element-wise multiplication (SIMD-accelerated).
/// Element-wise addition (SIMD-accelerated).