Install Node via apk on musl runners instead of nodejs.org's glibc tarball

Same runner dotnet-install.sh detects as musl and picks linux-musl-x64 for -
the glibc node tarball can't even exec there ("env: can't execute 'node'").

scripts/ci/lib.sh

@@ -91,6 +91,20 @@ ensure_node() {
     return 0
   fi
 
+  # nodejs.org only ships glibc binaries; on a musl/Alpine runner (same one
+  # dotnet-install.sh detects and picks the linux-musl-x64 SDK for) that
+  # tarball fails to exec at all ("env: can't execute 'node'"). Prefer the
+  # distro's own package on musl instead of a broken glibc download.
+  if [[ ! -x "$CI_ROOT/.node/bin/node" ]] && command -v apk > /dev/null 2>&1; then
+    log "node not found on PATH; installing via apk (musl runner)"
+    local sudo_cmd=""
+    if [[ "$(id -u)" -ne 0 ]] && command -v sudo > /dev/null 2>&1; then
+      sudo_cmd="sudo"
+    fi
+    $sudo_cmd apk add --no-cache nodejs npm
+    return 0
+  fi
+
   local node_version="22.14.0"
   local install_dir="$CI_ROOT/.node"
   if [[ ! -x "$install_dir/bin/node" ]]; then