Add cross-link to centralized MEAI documentation hub

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: HavenDV

docs/guides/meai.md

@@ -1,5 +1,8 @@
 # Microsoft.Extensions.AI Integration
 
+!!! tip "Cross-SDK comparison"
+    See the [centralized MEAI documentation](https://tryagi.github.io/docs/meai/) for feature matrices and comparisons across all tryAGI SDKs.
+
 The AI21 SDK implements `IChatClient` from [Microsoft.Extensions.AI](https://learn.microsoft.com/en-us/dotnet/ai/microsoft-extensions-ai), providing a unified interface for chat completions with text, streaming, tool calling, and reasoning support.
 
 ## Installation