feat: add quick command reference to guide, SSH support, and handoff doc

- Add copy-paste command reference card to guide.html Linux section
- Add enable-ssh.sh standalone script for remote access on Live USB
- Add optional SSH install prompt to setup-openclaw.sh
- Add HANDOFF.md for Mac mini Claude Code remote takeover

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

bootable/linux-setup/enable-ssh.sh

@@ -0,0 +1,31 @@
+#!/usr/bin/env bash
+# ============================================================
+#  Enable SSH server on Ubuntu Live USB
+#  Usage: sudo bash enable-ssh.sh
+# ============================================================
+set -euo pipefail
+
+if [[ $EUID -ne 0 ]]; then
+    echo "Usage: sudo bash enable-ssh.sh"
+    exit 1
+fi
+
+echo "Installing OpenSSH server..."
+apt-get update -qq
+apt-get install -y -qq openssh-server
+
+systemctl enable ssh
+systemctl start ssh
+
+REAL_USER="${SUDO_USER:-$USER}"
+echo ""
+echo "Set a password for SSH login (user: $REAL_USER):"
+passwd "$REAL_USER"
+
+LOCAL_IP=$(ip -4 addr show | grep -oP '(?<=inet\s)(?!127\.)\d+\.\d+\.\d+\.\d+' | head -1)
+echo ""
+echo "========================================"
+echo "  SSH Ready!"
+echo "  From Mac mini or other computer:"
+echo "  ssh ${REAL_USER}@${LOCAL_IP}"
+echo "========================================"