copy engram_vindex ANN module onto tiered trunk (staged->committed; not yet wired)

engram/test/run_vindex_tests.sh

@@ -0,0 +1,25 @@
+#!/bin/sh
+# Build + RUN the M8 HNSW vector-index tests. Pure C11 (gcc/cc), stdlib + libm
+# only. This is a standalone C module — NOT folded through elb/elc.
+#
+# Two passes:
+#   1. PERF  — optimised (-O2, no sanitizer): the real recall@10 gate + speedup
+#              numbers at full size (N=5000 recall, N=5000/20000 speedup).
+#   2. SAFETY — ASan + UBSan on the same suite at reduced size (VINDEX_QUICK=1);
+#              memory-safety is size-independent, so this stays fast.
+set -e
+HERE=$(cd "$(dirname "$0")" && pwd)
+RT="$HERE/../../lang/runtime"
+CC=${CC:-cc}
+SRC="$HERE/test_vindex.c $RT/engram_vindex.c $RT/engram_store.c"
+WARN="-std=c11 -Wall -Wextra"
+TMP=$(mktemp -d)
+
+echo "### PASS 1: PERF (optimised, un-sanitised) — recall gate + speedup"
+$CC $WARN -O2 -I"$RT" $SRC -lm -o "$TMP/perf"
+"$TMP/perf"
+
+echo
+echo "### PASS 2: SAFETY (ASan/UBSan, reduced size)"
+$CC $WARN -O1 -g -fsanitize=address,undefined -fno-omit-frame-pointer -I"$RT" $SRC -lm -o "$TMP/safe"
+VINDEX_QUICK=1 ASAN_OPTIONS=${ASAN_OPTIONS:-detect_leaks=0} UBSAN_OPTIONS=halt_on_error=1 "$TMP/safe"