ffmpeg opens all inputs before processing; input 1 is the audio FIFO. The
bridge previously opened the FIFO writer only after VHD_OpenStreamHandle +
VHD_StartStream succeeded, returning early on failure / no embedded audio and
never opening the FIFO -> ffmpeg blocked forever on input 1 -> 0 fps and an
empty HLS preview. Now the FIFO writer is opened unconditionally and first,
and the audio thread feeds a continuous, wall-clock-paced s16le stereo stream
(real samples when available, otherwise silence). SIGPIPE is ignored so a
dying ffmpeg returns EPIPE instead of killing the bridge.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
