WIP: support grpc policy attachment

[npolshakova]

Description

Follow up to #13281 which resolves status correctly on ancestorRef.

Fixes: #13161 (and supports all policies!)

Change Type

/kind feature

Changelog

Added support for GRPCRoute attached policy.

Additional Notes

Now that kind is respected on the route target and route name, HTTPRoute and GRPCRoute should be distinguished on the dataplane side: agentgateway/agentgateway#832

Show GRPCRoute does have transformation policy applied:

grpcurl -plaintext -authority example.com -vv gateway:80 yages.Echo/Ping 

Resolved method descriptor: rpc Ping ( .yages.Empty ) returns ( .yages.Content ); 

Request metadata to send: (empty) 

Response headers received: 
content-type: application/grpc date: Wed, 14 Jan 2026 16:03:27 GMT 
x-grpc-response: from-grpc 

Estimated response size: 6 bytes Response contents: { "text": "pong" } 

Response trailers received: (empty) 

Sent 0 requests and received 1 response

Show HTTPRoute does not have transformation policy applied:

k port-forward -n agentgateway-base svc/gateway 8080:80

❯ curl -v localhost:8080/ -H 'Host: example.com' 
* Host localhost:8080 was resolved.
* IPv6: ::1
* IPv4: 127.0.0.1
*   Trying [::1]:8080...
* Connected to localhost (::1) port 8080
* using HTTP/1.x
> GET / HTTP/1.1
> Host: example.com
> User-Agent: curl/8.13.0
> Accept: */*
> 
* Request completely sent off
< HTTP/1.1 200 OK
< date: Wed, 14 Jan 2026 16:10:47 GMT
< content-length: 191
< content-type: text/plain; charset=utf-8
< 
ServiceVersion=
ServicePort=80
Host=example.com
URL=/
Method=GET
Proto=HTTP/1.1
IP=10.244.0.14
RequestHeader=Accept:*/*
RequestHeader=User-Agent:curl/8.13.0
Hostname=backend-6bbdcd4675-zltbg
* Connection #0 to host localhost left intact