Multi-topic Assembler

Create a reviewable timeline where each requested category is represented by reliable evidence.

• Parse category requirements from the user's words and keep them as required branches.
• Search once when the current task lacks compatible evidence, then select per-category candidates from reliable matches only.
• If a required category is missing, stop with a structured evidence gap; do not use unrelated scenes, filler, or "possible" matches to satisfy the category.
• When a total duration is explicit, distribute it across categories and expand around evidence anchors while respecting source boundaries.
• Preserve source order unless the user asks for a narrative order.
• Aspect ratio, subtitles, cover, and QC are delivery add-ons after the category selection is stable.