fix(desktop): don't exec startx — fall back to shell on X failure

If X fails to start, the user gets a working shell prompt instead
of a dead session or autologin loop.

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

iso/overlay/home/bee/.profile

@@ -4,5 +4,7 @@ export PATH="/usr/local/bin:$PATH"
 # so the KVM shows the graphical UI without switching VTs.
 if [ "$(tty 2>/dev/null)" = "/dev/tty1" ] \
     && [ -z "${DISPLAY:-}" ]; then
-    exec startx /usr/local/bin/bee-openbox-session -- :0 vt1 -nolisten tcp
+    startx /usr/local/bin/bee-openbox-session -- :0 vt1 -nolisten tcp
+    echo ""
+    echo "X session ended. Type 'startx' to retry or use the shell."
 fi