The fundamental issue: mxlSleepUntil/mxlSleepForNs blocks the entire
thread, making LWS unresponsive and causing control commands to hang.
Meanwhile, LWS poll(1) adds latency that makes grain timing unreliable.
Solution: run node->process() in a dedicated thread that can freely use
mxlSleepUntil for precise grain timing, while the main thread runs
control_server->poll(10) for LWS event handling.
Passthrough now uses mxlSleepUntil(deadline) matching the mxl-gst-sink
Cursor pattern, with 2-grain read delay for buffering.
Johanness
5b48d86c6e