chore: import upstream snapshot with attribution

.github/scripts/download_opt125m_github.sh

@@ -0,0 +1,58 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: Apache-2.0
+#
+# Download facebook/opt-125m from the LMCache/opt-125m GitHub release
+# and place it into the HuggingFace hub cache structure so vLLM can
+# find it via ``facebook/opt-125m`` without any network call to HF.
+#
+# Environment:
+#   OPT125M_GH_RELEASE  release tag (default: v1.0)
+#   OPT125M_SNAPSHOT    HF snapshot hash (default: 27dcfa...)
+
+set -euo pipefail
+
+GH_RELEASE="${OPT125M_GH_RELEASE:-v1.0}"
+SNAPSHOT="${OPT125M_SNAPSHOT:-27dcfa74d334bc871f3234de431e71c6eeba5dd6}"
+
+HF_CACHE="${HF_HOME:-$HOME/.cache/huggingface}/hub"
+MODEL_DIR="${HF_CACHE}/models--facebook--opt-125m"
+SNAPSHOT_DIR="${MODEL_DIR}/snapshots/${SNAPSHOT}"
+
+if [ -f "${SNAPSHOT_DIR}/pytorch_model.bin" ]; then
+    echo "opt-125m already cached in ${SNAPSHOT_DIR}, skipping download"
+    exit 0
+fi
+
+echo "Downloading opt-125m from GitHub release ${GH_RELEASE}..."
+mkdir -p "${SNAPSHOT_DIR}"
+
+TMP_DIR="$(mktemp -d)"
+trap 'rm -rf "${TMP_DIR}"' EXIT
+
+TARBALL="${TMP_DIR}/opt-125m.tar.gz"
+DOWNLOAD_URL="https://github.com/LMCache/opt-125m/releases/download/${GH_RELEASE}/opt-125m.tar.gz"
+
+for i in $(seq 1 5); do
+    if curl -fsSL --retry 3 -o "${TARBALL}" "${DOWNLOAD_URL}"; then
+        break
+    fi
+    if [ "${i}" -eq 5 ]; then
+        echo "!! Failed to download after 5 attempts: ${DOWNLOAD_URL}"
+        exit 1
+    fi
+    sleep $((10 * i))
+done
+
+# Extract directly – the tarball contains opt-125m/ at top level.
+EXTRACT_DIR="${TMP_DIR}/extract"
+mkdir -p "${EXTRACT_DIR}"
+tar -xzf "${TARBALL}" -C "${EXTRACT_DIR}"
+mv "${EXTRACT_DIR}"/opt-125m/* "${SNAPSHOT_DIR}/"
+
+# Create the refs/main pointer so snapshot_download(local_files_only=True)
+# can resolve the snapshot hash.
+mkdir -p "${MODEL_DIR}/refs"
+echo "${SNAPSHOT}" > "${MODEL_DIR}/refs/main"
+
+echo "opt-125m cached at ${SNAPSHOT_DIR}"
+ls -lah "${SNAPSHOT_DIR}/"