clawmates: phase work

Mission: 01a00c41-bac0-7eb3-a8c8-8b7044f3086d
Phase: 01a00c41-bac2-71e3-a58b-c473421200ee

Committed by the ClawMates delivery pipeline from the agents' working tree. Authored by agents, not by the named committer.

crates/clawhdf5-ann/src/hnsw.rs

@@ -44,32 +44,14 @@ impl DistanceMetric {
 }
 
 /// Compute distance between two vectors using the given metric.
+///
+/// Delegates to `clawhdf5-accel`'s runtime-dispatched SIMD kernels (AVX2 on
+/// x86_64, NEON on aarch64, portable scalar fallback elsewhere) — this is
+/// the hottest loop in both HNSW build and every `hybrid_search` query.
 fn compute_distance(a: &[f32], b: &[f32], metric: DistanceMetric) -> f32 {
     match metric {
-        DistanceMetric::L2 => {
-            let mut sum = 0.0f32;
-            for i in 0..a.len() {
-                let d = a[i] - b[i];
-                sum += d * d;
-            }
-            sum.sqrt()
-        }
-        DistanceMetric::Cosine => {
-            let mut dot = 0.0f32;
-            let mut norm_a = 0.0f32;
-            let mut norm_b = 0.0f32;
-            for i in 0..a.len() {
-                dot += a[i] * b[i];
-                norm_a += a[i] * a[i];
-                norm_b += b[i] * b[i];
-            }
-            let denom = norm_a.sqrt() * norm_b.sqrt();
-            if denom < f32::EPSILON {
-                1.0
-            } else {
-                1.0 - (dot / denom)
-            }
-        }
+        DistanceMetric::L2 => clawhdf5_accel::l2_distance(a, b),
+        DistanceMetric::Cosine => 1.0 - clawhdf5_accel::cosine_similarity(a, b),
     }
 }