API: Share of Voice, Models Filter & Docs Search in Agent Chat

The REST v2 API and MCP server now return the same share of voice you see on the dashboard, on the responses summary and brand visibility endpoints. Response analytics and query fan-outs accept a models filter, and citation rank comes back as a 1-based answer position. Agent Chat can also search the Promptwatch docs, so questions about how a feature works get answered from the documentation instead of a guess.