test(vectorindex): skip Recall10k under -race (#32)

TestHNSW_Recall10k is the CI bottleneck at ~410s under -race (68% of
the integration job). The workload is fully sequential — build 10k
vectors, then 20 query probes — so the race detector has nothing to
catch and just adds ~10× overhead.

Added a raceEnabled build-tagged constant (standard Go idiom) so the
test skips only under -race. TestHNSW_ConcurrentAddSearch still runs
under -race and covers the actual concurrent code path.

Local timings:
  go test -run Recall10k            68s (recall=1.000)
  go test -race -run Recall10k       1s (skip)
  go test -race -run ConcurrentAdd   2s (unchanged)

Integration CI projected: 600s → ~190s.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: aksOps

internal/vectorindex/hnsw_test.go

@@ -215,6 +215,13 @@ func TestHNSW_Recall10k(t *testing.T) {
 	if testing.Short() {
 		t.Skip("skipping 10k benchmark in -short")
 	}
+	if raceEnabled {
+		// Workload is fully sequential (no goroutines), so the race
+		// detector has nothing to catch here — it just adds ~10× overhead
+		// that dominates CI. Concurrency correctness is covered by
+		// TestHNSW_ConcurrentAddSearch, which DOES run under -race.
+		t.Skip("skipping 10k recall benchmark under -race (sequential workload)")
+	}
 	const (
 		n   = 10_000
 		dim = 384

internal/vectorindex/race_off.go

@@ -0,0 +1,5 @@
+//go:build !race
+
+package vectorindex
+
+const raceEnabled = false

internal/vectorindex/race_on.go

@@ -0,0 +1,10 @@
+//go:build race
+
+package vectorindex
+
+// raceEnabled reports whether the package was compiled with -race.
+// Some long-running deterministic benchmarks (e.g. TestHNSW_Recall10k)
+// gain nothing from the race detector — they're sequential — and pay
+// ~10× overhead that dominates CI time. Those tests skip when this is
+// true, leaving the explicitly concurrent tests to exercise the detector.
+const raceEnabled = true