[Fix] install.sh: nvm_check_global_modules: don't run a Windows npm under WSL

Under WSL, `PATH` can include a Windows Node install, so `command -v npm` can find its `npm` shell shim, which then failed against Windows paths.
That npm is not a system node that nvm would shadow, so under WSL, skip an npm that has an `npm.cmd` beside it: both the Node installer and npm's own shims put one there.
Outside WSL (eg, Git Bash or Cygwin), a Windows npm is the system node, so the warning is kept.

Fixes #3700.

Signed-off-by: NUAAwqy <146524024+NUAAwqy@users.noreply.github.com>
Co-Authored-By: Codex <noreply@openai.com>

test/install_script/nvm_check_global_modules

@@ -5,11 +5,12 @@ cleanup () {
   unset npm_config_prefix
 
   rm -f npm
+  [ -z "${WINDOWS_NPM_DIR-}" ] || rm -rf "${WINDOWS_NPM_DIR}"
   PATH="$ORIGINAL_PATH"
   NVM_DIR="$ORIGINAL_NVM_DIR"
 
   unset -f setup cleanup die
-  unset message ORIGINAL_PATH ORIGINAL_NVM_DIR
+  unset message ORIGINAL_PATH ORIGINAL_NVM_DIR WINDOWS_NPM_DIR
 }
 die () { echo "$@" ; cleanup ; exit 1; }
 
@@ -61,5 +62,26 @@ chmod +x npm
 message=$(nvm_check_global_modules)
 [ -z "$message" ] || die "nvm_check_global_modules should have not printed a notice when npm was unavailable; got:\n${message}"
 
+# Faking a Windows Node's npm, with a global module installed
+WINDOWS_NPM_DIR="$(mktemp -d)"
+cat <<'SH' >"${WINDOWS_NPM_DIR}/npm"
+#!/bin/sh
+case "$1" in
+  --version) echo '10.0.0' ;;
+  list) printf '%s\n' 'npm@10.0.0' '└── windows-global@1.0.0' ;;
+esac
+SH
+touch "${WINDOWS_NPM_DIR}/npm.cmd"
+chmod +x "${WINDOWS_NPM_DIR}/npm"
+PATH="${WINDOWS_NPM_DIR}:${ORIGINAL_PATH}"
+
+nvm_is_wsl() { return 0; }
+message=$(nvm_check_global_modules)
+[ -z "$message" ] || die "nvm_check_global_modules should not run a Windows npm under WSL; got:\n${message}"
+
+nvm_is_wsl() { return 1; }
+message=$(nvm_check_global_modules)
+[ -n "$message" ] || die 'nvm_check_global_modules should still warn about a Windows npm outside WSL, where it is the system node'
+
 
 cleanup