Add AI Chat guide

[alexkorep]

Summary

Added AI Chat in the ClickHouse Cloud guide.

Checklist

• Delete items not relevant to your PR
• URL changes should add a redirect to the old URL via https://github.com/ClickHouse/clickhouse-docs/blob/main/docusaurus.config.js
• If adding a new integration page, also add an entry to the integrations list here: https://github.com/ClickHouse/clickhouse-docs/blob/main/docs/integrations/index.mdx

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[Copilot]

Pull Request Overview

This PR adds comprehensive documentation for the AI Chat feature in ClickHouse Cloud Console. The guide provides step-by-step instructions for enabling, configuring, and using the AI Chat functionality within the Cloud interface.

• Complete user guide covering AI Chat setup, usage patterns, and keyboard shortcuts
• Documentation of two chat modes: Agent (schema reasoning) and Docs AI (documentation Q&A)
• Integration workflow examples showing how to work with generated SQL queries

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Project	Deployment	Preview	Comments	Updated (UTC)
clickhouse-docs	Ready	Preview		Sep 18, 2025 2:34pm

2 Skipped Deployments

Project	Deployment	Preview	Comments	Updated (UTC)
clickhouse-docs-ru	Ignored	Preview		Sep 18, 2025 2:34pm
clickhouse-docs-zh	Ignored	Preview		Sep 18, 2025 2:34pm