VNC reliability
- Restore initial VNC attachment for Xvfb launched with
-displayfd. - Preserve per-server display ownership across multi-instance hosts.
- Reattach x11vnc after browser/Xvfb restarts on the same display.
- Add
GET /vnc/statusfor attachment and port discovery. - Add hermetic watcher coverage and a disposable Linux recovery smoke test.
Includes the VNC work proposed in #4781, #5243, #6549, and #8070. Thanks @Doud-FR, @paranoidi, @modanq, and @luxles.