Change default Node runtime from 18 to 20

Author: mengyimicro

Readme-Usage.md

@@ -398,7 +398,7 @@ a365 setup  # Creates agent blueprint and registers messaging endpoint
 Choose based on your application type:
 
 - **.NET Projects:** .NET 8.0 SDK or later
-- **Node.js Projects:** Node.js (18+ recommended) and npm
+- **Node.js Projects:** Node.js (20+ recommended) and npm
 - **Python Projects:** Python 3.11+ and pip
 
 The CLI will validate that required tools are installed before deployment.

src/Microsoft.Agents.A365.DevTools.Cli/Commands/SetupSubcommands/InfrastructureSubcommand.cs

@@ -652,7 +652,7 @@ private static string GetRuntimeForPlatform(Models.ProjectPlatform platform)
         return platform switch
         {
             Models.ProjectPlatform.Python => "PYTHON:3.11",
-            Models.ProjectPlatform.NodeJs => "NODE:18-lts", 
+            Models.ProjectPlatform.NodeJs => "NODE:20-lts", 
             Models.ProjectPlatform.DotNet => "DOTNETCORE:8.0",
             _ => "DOTNETCORE:8.0" // Default fallback
         };