fix(cli): pass converted cwd to spawn in shadowNpmBase

The URL-to-path conversion was happening but the converted string wasn't
being passed to spawn. The spawn call received the original URL object in
spawnOpts instead of the converted path string.

This fix explicitly passes the converted cwd to spawn options, ensuring
URL-based cwd values work correctly across all platforms.

Fixes the "should handle URL cwd option" test failure.

Author: jdalton

packages/cli/src/shadow/npm-base.mts

@@ -187,6 +187,7 @@ export default async function shadowNpmBase(
     ],
     {
       ...spawnOpts,
+      cwd,
       env: {
         ...process.env,
         ...spawnEnv,