Function l2_from_dot

nodedb-codec/src/vector_quant/ternary/codec.rs:50–52

`‖a·sa - b·sb‖² ≈ sa²·‖a‖² + sb²·‖b‖² - 2·sa·sb·dot(a,b)`

(dot: i32, norm_a: f32, norm_b: f32, sa: f32, sb: f32)

/// `‖a·sa - b·sb‖² ≈ sa²·‖a‖² + sb²·‖b‖² - 2·sa·sb·dot(a,b)`
fn l2_from_dot(dot: i32, norm_a: f32, norm_b: f32, sa: f32, sb: f32) -> f32 {
    (norm_a + norm_b - 2.0 * sa * sb * dot as f32).max(0.0)
}

/// Expand cold-packed bits to hot if needed.
fn ensure_hot(packed: &[u8], quant_mode: u16, dim: usize) -> std::borrow::Cow<'_, [u8]> {