Add update.sh to generated project scripts

Updates three things:
1. Context Studio Core — git pull on ~/.context-studio/core
2. Claude Code — npm install -g @anthropic-ai/claude-code in container
3. OS packages — apt-get update + upgrade in container

If container is not running, in-container steps are skipped with a warning.
Offers optional full image rebuild (--pull --no-cache) for a clean slate.
Warns that in-container updates are ephemeral without a rebuild.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

wizard.sh

@@ -137,6 +137,11 @@ print_next_steps() {
     echo -e "${BOLD}Stop the container:${RESET}"
     echo -e "  ${CYAN}./stop.sh${RESET}"
     echo ""
+    echo -e "${BOLD}Update everything:${RESET}"
+    echo -e "  ${CYAN}./update.sh${RESET}"
+    echo -e "  Updates Context Studio Core, Claude Code, and OS packages."
+    echo -e "  Optionally rebuilds the image from scratch."
+    echo ""
     echo -e "${BOLD}How it works:${RESET}"
     echo -e "  • Context Studio Core runs on your host (Electron UI, no display issues)"
     echo -e "  • Claude Code agents run inside container ${CYAN}cs-${slug}${RESET}"