fix: use shell mode on Windows for command spawning

On Windows, spawn("npm", [...]) fails with ENOENT because Windows
requires .cmd/.exe extensions or shell-based PATH resolution.
Adding shell: true on Windows enables proper PATH lookup for npm
and other commands spawned via runCommandWithTimeout.

Fixes #4557

Co-Authored-By: Ayush Ojha <ayushozha@outlook.com>

src/process/exec.ts

@@ -80,11 +80,13 @@ export async function runCommandWithTimeout(
   }
 
   const stdio = resolveCommandStdio({ hasInput, preferInherit: true });
+  const isWindows = process.platform === "win32";
   const child = spawn(argv[0], argv.slice(1), {
     stdio,
     cwd,
     env: resolvedEnv,
     windowsVerbatimArguments,
+    shell: isWindows,
   });
   // Spawn with inherited stdin (TTY) so tools like `pi` stay interactive when needed.
   return await new Promise((resolve, reject) => {