Enhance documentation with video and Cosmos DB benefits

Added a video introduction and expanded on the benefits of using Azure Cosmos DB for AI workloads, emphasizing its global distribution and low-latency performance.

Author: staleycyn

learn-pr/wwl-azure/manage-secure-ai-ready-infrastructure/includes/4-deploy-azure-cosmos-agent.md

@@ -1,3 +1,7 @@
+The video introduces the key concepts covered on this page. 
+
+> [!VIDEO https://learn-video.azurefd.net/vod/player?id=a5b25f01-eb41-43b2-9660-d00260317614]
+
 Your AI agent now authenticates to Azure services using managed identities without storing any credentials, and RBAC roles enforce least-privilege access to backend resources. However, the agent still needs a durable store for conversation history that supports real-time queries while maintaining regulatory compliance. Traditional relational databases struggle with the unpredictable query patterns and global distribution requirements of AI workloads—chatbot sessions spike during business hours across different time zones, users expect instant access to conversation history from any device, and compliance teams mandate automatic data expiration after 90 days to satisfy regulations.
 
 Azure Cosmos DB for NoSQL addresses these challenges by providing a globally distributed, low-latency database optimized for document storage and flexible querying. Unlike traditional databases that require complex sharding strategies and manual replication configuration, Cosmos DB distributes your data automatically across Azure regions with single-digit millisecond read and write latency at the 99th percentile. This performance becomes critical when your AI agent retrieves conversation context to generate personalized responses—a 500-ms database query delay translates directly to noticeable lag in the chat interface, degrading user experience, and reducing task completion rates by 25% according to Contoso's user research.