Mutation - addCampaignResearchColumn

Adds an AI research column to the campaign table. With researchExisting (default true) it queues research for every person already in the table; people added later are researched only when their add asks for it. Each person's research uses Buzz AI credits. With lookbackDays, only evidence from that many days before each run counts, so a rerun refreshes the column (for example recent news). With webSearch, the prompt is an open-ended request Buzz answers by searching the public web for each person, such as their talks, publications or published content; the cell sums up what it found and the details list each asset with its link. It runs a few people at a time. Access: caller must have CRM access to the campaign workspace. Errors: missing campaign, empty label or prompt, a lookbackDays other than 30, 90 or 180, exhausted Buzz AI credits, or rate limit.