Rebuild local Blender WASM environment and recovery evidence

tools/web/prepare-emscripten.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+emsdk_dir="${EMSDK_ROOT:-${repo_root}/.emsdk}"
+emsdk_url="${EMSDK_URL:-https://gh-proxy.com/https://github.com/emscripten-core/emsdk/archive/refs/heads/main.tar.gz}"
+
+if [[ ! -x "${emsdk_dir}/emsdk" ]]; then
+  archive="$(mktemp --suffix=.tar.gz)"
+  trap 'rm -f "${archive}"' EXIT
+  curl -L --fail --retry 3 --max-time 180 "${emsdk_url}" -o "${archive}"
+  mkdir -p "${emsdk_dir}"
+  tar -xzf "${archive}" --strip-components=1 -C "${emsdk_dir}"
+fi
+
+cd "${emsdk_dir}"
+./emsdk install 3.1.69
+./emsdk activate 3.1.69
+source ./emsdk_env.sh
+emcc --version | head -3
+printf 'emscripten-ready root=%s version=%s\n' "${emsdk_dir}" "$(emcc --version | awk 'NR==1 {print $NF}')"