yt-ingestion: standalone artifact fetcher

When triggered, invoke the yt-ingestion-agent sub-agent with:

• youtube_url: the URL from the user's message
• output_dir: by default, Team/BenAI/Profiles/Milan/Daily/{today}/yt-ingestion-{video-id}/. If the user specifies an output directory, use theirs.

Surface the resulting manifest path to the user when done. If the agent surfaces a 3-option choice (e.g., 1080p blocked), present those options to the user and pass their selection back.

Profile boundary

Output writes to Profiles/Milan/. See [[yt-pipeline SPEC|SPEC.md]] for the full invariant.

When NOT to use this skill

• The user wants a full course package: use yt-to-course instead.
• The user wants a community announcement post: use yt-to-community instead.

For details on the fallback chain, see [[fallback-strategies]].