chore: import upstream snapshot with attribution

scripts/validate-nlt-coverage.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+set -euo pipefail
+cd "$(git rev-parse --show-toplevel)"
+missing=()
+for id in NL-0 NL-1 NL-2 NL-3 NL-4 T-A T-B T-C T-D T-E T-F T-G T-H T-I T-J; do
+  [[ -s "reports/${id}_results.xml" ]] || missing+=("$id")
+done
+if (( ${#missing[@]} )); then
+  echo "Missing fragments: ${missing[*]}"
+  exit 2
+fi
+echo "All NL/T fragments present."