Feedback ffmpeg nostdin ssh heredoc fix

When running ffmpeg via ssh host bash -s with a heredoc-fed script, ffmpeg polls stdin for interactive keypress shortcuts. This causes it to thrash reading the heredoc pipe, resulting in billions of syscalls and near-zero throughput (e.g. 45 min to process what takes 2 min standalone).

Fix: always pass -nostdin to ffmpeg in any non-interactive/scripted invocation. This was confirmed in a Plex audio re-encode batch where removing stdin polling restored full throughput immediately (250 MB/min vs effectively 0).

Why: ffmpeg's default behavior assumes an interactive terminal and polls stdin continuously. SSH heredoc feeds are not TTYs, so this devolves into a syscall storm.

How to apply: Any ffmpeg command run via nohup, ssh pipe, systemd unit, or scripted heredoc must include -nostdin as an early flag. Add it to all forge ffmpeg wrappers and batch scripts.

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