Content Agent: Meta Titles & Page Tracker Filter

Articles now have a separate meta title. The editor labels the old title as H1 and adds a meta title field that falls back to the H1 when empty. Webflow and Framer field mappings can point at it, and it comes back in the REST v2 and MCP content responses. Page Tracker can filter to pages that came out of the Content Agent, and the competitor picker in the content brief shows how many unique citations each competitor has for the selected prompt.