Add headless Agentbox environment spike

Co-authored-by: codegirl007 <codegirl-007@users.noreply.github.com>

agentbox/environment/entrypoint.sh

@@ -0,0 +1,44 @@
+#!/bin/sh
+set -eu
+
+export HOME=/tmp/home
+export XDG_RUNTIME_DIR=/tmp/runtime
+mkdir -p "$HOME" "$XDG_RUNTIME_DIR"
+chmod 0700 "$XDG_RUNTIME_DIR"
+
+cleanup() {
+    rm -f /tmp/agentbox-ready
+    kill "${OPENBOX_PID:-}" "${XVFB_PID:-}" 2>/dev/null || true
+    wait "${OPENBOX_PID:-}" "${XVFB_PID:-}" 2>/dev/null || true
+}
+
+terminate() {
+    trap - EXIT INT TERM
+    cleanup
+    exit 0
+}
+
+trap cleanup EXIT
+trap terminate INT TERM
+
+Xvfb "$DISPLAY" -screen 0 640x480x24 -nolisten tcp -noreset &
+XVFB_PID=$!
+
+attempt=0
+until xdpyinfo -display "$DISPLAY" >/dev/null 2>&1; do
+    attempt=$((attempt + 1))
+    if [ "$attempt" -ge 100 ]; then
+        echo "Xvfb did not become ready" >&2
+        exit 1
+    fi
+    sleep 0.05
+done
+
+openbox --sm-disable >/tmp/openbox.log 2>&1 &
+OPENBOX_PID=$!
+touch /tmp/agentbox-ready
+
+while :; do
+    sleep 3600 &
+    wait $!
+done