Plan subtitle emphasis marks for semantic item `{semantic_item_id}`.

## Product context
Title: {title}
Summary: {summary}

## Allowed styles
{subtitle_style_catalog}
Choose simplest matching style; reserve stronger looks for true peaks, urgency, or standout words.

## Indexed transcript
Each line: [segment_id] [start_seconds-end_seconds] index:word ...
Each returned mark must point to exactly one indexed word via `word_index`.

{indexed_transcript}