update a2a sample to work with latest a2a library (#1149)

dotnet/samples/A2AClientServer/A2AServer/A2AServer.http

@@ -4,7 +4,7 @@
 @hostLogistics = http://localhost:5002
 
 ### Query agent card for the invoice agent
-GET {{hostInvoice}}/.well-known/agent.json
+GET {{hostInvoice}}/.well-known/agent-card.json
 
 ### Send a message to the invoice agent
 POST {{hostInvoice}}
@@ -17,6 +17,7 @@ Content-Type: application/json
     "params": {
         "id": "12345",
         "message": {
+            "kind": "message",
             "role": "user",
             "messageId": "msg_1",
             "parts": [
@@ -30,7 +31,7 @@ Content-Type: application/json
 }
 
 ### Query agent card for the policy agent
-GET {{hostPolicy}}/.well-known/agent.json
+GET {{hostPolicy}}/.well-known/agent-card.json
 
 ### Send a message to the policy agent
 POST {{hostPolicy}}
@@ -43,6 +44,7 @@ Content-Type: application/json
     "params": {
         "id": "12345",
         "message": {
+            "kind": "message",
             "role": "user",
             "messageId": "msg_1",
             "parts": [
@@ -56,7 +58,7 @@ Content-Type: application/json
 }
 
 ### Query agent card for the logistics agent
-GET {{hostLogistics}}/.well-known/agent.json
+GET {{hostLogistics}}/.well-known/agent-card.json
 
 ### Send a message to the logistics agent
 POST {{hostLogistics}}
@@ -69,6 +71,7 @@ Content-Type: application/json
     "params": {
         "id": "12345",
         "message": {
+            "kind": "message",
             "role": "user",
             "messageId": "msg_1",
             "parts": [

dotnet/samples/A2AClientServer/A2AServer/Program.cs

@@ -103,5 +103,6 @@ else
 }
 
 app.MapA2A(hostAgent!.TaskManager!, "/");
+app.MapWellKnownAgentCard(hostAgent!.TaskManager!, "/");
 
 await app.RunAsync();

dotnet/samples/A2AClientServer/README.md

@@ -108,7 +108,7 @@ This sample contains a [.http file](https://learn.microsoft.com/aspnet/core/test
 1. In Visual Studio open [./A2AServer/A2AServer.http](./A2AServer/A2AServer.http)
 1. There are two sent requests for each agent, e.g., for the invoice agent:
     1. Query agent card for the invoice agent
-        `GET {{hostInvoice}}/.well-known/agent.json`
+        `GET {{hostInvoice}}/.well-known/agent-card.json`
     1. Send a message to the invoice agent
         ```
         POST {{hostInvoice}}
@@ -121,6 +121,7 @@ This sample contains a [.http file](https://learn.microsoft.com/aspnet/core/test
             "params": {
                 "id": "12345",
                 "message": {
+                    "kind": "message",
                     "role": "user",
                     "messageId": "msg_1",
                     "parts": [