FFmpeg subtitle titles can trigger MP4 UDTA parsing warnings

With FFmpeg 9.0.1, copying text-subtitle title tags into MP4 generated the warning "UDTA parsing failed retrying raw". Controlled short remuxes isolated it to subtitle titles: clear each title with -metadata:s:s:N title= and preserve its label using -metadata:s:s:N handler_name=LABEL; language metadata remains. Keep video/audio on stream copy and subtitles on mov_text, then verify copied media hashes and extracted subtitle dialogue/timing before publishing.