bug: acp integration with intellij no longer works since update to kiro-cli 1.28.1

### Checks

- [x] I have searched [github.com/aws/amazon-q-developer-cli/issues](https://github.com/aws/amazon-q-developer-cli/issues?q=) and there are no duplicates of my issue
- [x] I have run `q doctor` in the affected terminal session
- [x] I have run `q restart` and replicated the issue again

### Operating system

osx

### Expected behaviour

https://kiro.dev/docs/cli/acp/

acp integration used to work as per above instructions until update this week

### Actual behaviour

get an error in intellij: `method not found: authenticate`

found this in acp logs
```
2026-03-25 09:55:28,076 [5033535] FINER - #c.i.m.l.a.a.e.AcpIdeaMcpProviderImpl - Running private IJ MCP session for agent acp.kiro
2026-03-25 09:55:28,076 [5033535] FINER - #c.i.m.l.a.a.e.AcpIdeaMcpProviderImpl - Awaiting cancellation of private IJ MCP session for agent acp.kiro
2026-03-25 09:55:28,076 [5033535] INFO - #c.i.m.l.a.a.c.a.AcpAuthenticationService - acp.kiro: get auth NONE
2026-03-25 09:55:29,182 [5034641] INFO - #c.i.m.l.a.a.p.AcpProcessHandlerService - Reusing existing process handler for agent 'Kiro' in chat 8de94113-1d33-43ac-8d91-e5641e0b1e5e
2026-03-25 09:55:31,868 [5037327] INFO - #c.i.m.l.a.a.c.a.AuthHandlerDispatcher - Using StandardAuthHandler for auth method: kiro-login
2026-03-25 09:55:31,868 [5037327] INFO - #c.i.m.l.a.a.c.a.StandardAuthHandler - Authenticating with standard method: kiro-login
2026-03-25 09:55:31,869 [5037328] WARN - #c.i.m.l.a.a.c.a.StandardAuthHandler - Standard authentication failed for method kiro-login
com.agentclientprotocol.protocol.JsonRpcException: Method not found
at com.agentclientprotocol.protocol.Protocol.handleResponse(Protocol.kt:465)
at com.agentclientprotocol.protocol.Protocol.handleIncomingMessage(Protocol.kt:366)
at com.agentclientprotocol.protocol.Protocol.access$handleIncomingMessage(Protocol.kt:122)
at com.agentclientprotocol.protocol.Protocol$start$2.invokeSuspend(Protocol.kt:172)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:34)
at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:100)
at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:610)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runDefaultDispatcherTask(CoroutineScheduler.kt:1194)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:906)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:775)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:762)
2026-03-25 09:55:31,869 [5037328] INFO - #c.i.m.l.a.a.p.AcpProcessHandlerService - Stopping process handler for agent acp.kiro in chat 8de94113-1d33-43ac-8d91-e5641e0b1e5e
2026-03-25 09:55:31,869 [5037328] INFO - #c.i.m.l.a.a.p.EelAcpProcessHandler - [Kiro] Stopping server
2026-03-25 09:55:31,869 [5037328] INFO - #c.i.m.l.a.a.p.AcpProcessHandlerService - Successfully stopped process handler for agent acp.kiro in chat
```

### Steps to reproduce

latest intellij ultimate, ai assistant plugin and kiro-cli as of 25th of march

### Environment

```yaml

```