Prepare isolated Qwen3.8 IQ4_XS A/B tests

experiments/qwen38-20260907-ab/download-candidate.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+set -Eeuo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+# shellcheck source=candidates.sh
+source "$SCRIPT_DIR/candidates.sh"
+candidate_config "${1:-}"
+
+target_dir="$MODEL_ROOT/$CANDIDATE_ID"
+target="$target_dir/$MODEL_FILE"
+partial="$target.part"
+
+install -d -m 0755 "$target_dir"
+
+if [[ -s $target ]]; then
+  printf '%s  %s\n' "$MODEL_SHA256" "$target" | sha256sum -c -
+  echo "Already prepared: $target"
+  exit 0
+fi
+
+echo "Downloading pinned $CANDIDATE_ID artifact ($MODEL_SIZE bytes)"
+curl --fail --location --retry 8 --retry-delay 5 --continue-at - \
+  --output "$partial" "$MODEL_URL"
+
+actual_size=$(stat -c %s "$partial")
+if [[ $actual_size != "$MODEL_SIZE" ]]; then
+  echo "Size mismatch: expected $MODEL_SIZE, got $actual_size; keeping $partial for inspection" >&2
+  exit 1
+fi
+printf '%s  %s\n' "$MODEL_SHA256" "$partial" | sha256sum -c -
+mv -f "$partial" "$target"
+echo "Prepared and verified: $target"