fix(shell): remove stray 'impo' typo causing ReferenceError

💘 Generated with Crush

Assisted-by: GLM-5.1 via Crush <crush@charm.land>

web/src/components/Shell.jsx

@@ -1,5 +1,4 @@
 import { useState, useRef, useEffect, useCallback } from 'react'
-impo
 // === Style thème système pour xterm ===
 function getCSSVariable(varName) {
   if (typeof document === 'undefined') return null;