When embedded-track extraction is skipped (network-mounted media), live mpv
text during per-glyph typeset karaoke is a wall of simultaneous one-glyph
lines plus the syllable being typed. No parsed cues exist to substitute, so
the wall reached both overlays and recording verbatim. Detect bursts of many
single-glyph lines in the live fallback paths and drop them with their short
syllable companions, keeping concurrent dialogue lines.