Add ClickHouse Agents docs with screenshots for recently shipped capabilities

Add or update docs (with screenshots) under docs/cloud/features/10_AI_ML/ for the following ClickHouse Agents capabilities:

• ClickHouse tool call UI — native rendering of MCP tool results as interactive charts, collapsible org/service rows, a virtualized query-result grid, a SQL query tab, and cost breakdowns.
• Context / token / cost usage gauge.
• Human-in-the-loop tool approval.
• Quote / reference selected chat text.
• Private chat projects.
• Agent API keys (Settings → Data controls).