Clear stale X display lock before starting Xvfb

A bot crash leaves /tmp/.X99-lock behind; the next container start
hits "Server is already active for display 99" and the entrypoint
previously fell through with only a warning, so Chromium then died
with "Missing X server or $DISPLAY" in a tight crash loop. Remove
the stale lock up-front and fail hard if Xvfb still won't come up,
so the failure mode is "container won't start" rather than "bot
crashes forever".

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

docker/entrypoint.sh

@@ -25,22 +25,30 @@ if [ ! -e "${NOVNC_WEB_DIR}/index.html" ] && [ -e "${NOVNC_WEB_DIR}/vnc.html" ];
   ln -sf vnc.html "${NOVNC_WEB_DIR}/index.html"
 fi
 
+# Clear any stale lock from a prior unclean exit — otherwise Xvfb refuses
+# to bind to the display and the bot starts up with no X server.
+rm -f "/tmp/.X${DISPLAY_NUM}-lock" "/tmp/.X11-unix/X${DISPLAY_NUM}" 2>/dev/null || true
+
 echo "[entrypoint] starting Xvfb on ${DISPLAY} (${GEOMETRY})"
 Xvfb "${DISPLAY}" -screen 0 "${GEOMETRY}" -ac +extension RANDR &
 XVFB_PID=$!
 
 # Give Xvfb a moment to come up. Requires x11-utils (xdpyinfo).
+XVFB_READY=0
 for i in $(seq 1 50); do
   if xdpyinfo -display "${DISPLAY}" >/dev/null 2>&1; then
     echo "[entrypoint] Xvfb is ready after ${i} checks"
+    XVFB_READY=1
     break
   fi
   sleep 0.2
-  if [ "${i}" = "50" ]; then
-    echo "[entrypoint] WARNING: Xvfb did not respond after 10s" >&2
-  fi
 done
 
+if [ "${XVFB_READY}" != "1" ]; then
+  echo "[entrypoint] FATAL: Xvfb did not respond after 10s — refusing to launch bot without a display" >&2
+  exit 1
+fi
+
 # Minimal window manager so dialogs and tabs aren't stuck behind the root window.
 if command -v fluxbox >/dev/null 2>&1; then
   fluxbox >/dev/null 2>&1 &