Missing WorkflowTaskTypeEnum values: AGENT, GET_AGENT_CARD, CANCEL_AGENT, PULL_WORKFLOW_MESSAGES

## Summary

Four task type enum values present in the Conductor server since 3.32.0-rc.9 are absent from `WorkflowTaskTypeEnum` in `Conductor/Client/Models/WorkflowTask.cs`. Users cannot reference these task types via the enum; deserialization of workflow definitions containing them may produce incorrect results.

Tested against: **Conductor OSS 3.32.0-rc.9**

## Missing Values

| Server TaskType | Notes |
|----------------|-------|
| `AGENT` | Run a conductor agent (A2A). Added in server PR #1288 / 3.32.0-rc.9. |
| `GET_AGENT_CARD` | Retrieve an agent card. Added in 3.32.0-rc.9. |
| `CANCEL_AGENT` | Cancel a running agent. Added in 3.32.0-rc.9. |
| `PULL_WORKFLOW_MESSAGES` | Pull messages from a workflow. |

Current enum ends at `WAITFORWEBHOOK = 30`. All four values are absent.

## Server Acceptance

Server acceptance confirmed for AGENT in JavaScript SDK audit against Conductor OSS 3.32.0-rc.9.

## Fix

Add to `WorkflowTaskTypeEnum`:

```csharp
[EnumMember(Value = "PULL_WORKFLOW_MESSAGES")]
PULLWORKFLOWMESSAGES = 31,

[EnumMember(Value = "AGENT")]
AGENT = 32,

[EnumMember(Value = "GET_AGENT_CARD")]
GETAGENTCARD = 33,

[EnumMember(Value = "CANCEL_AGENT")]
CANCELAGENT = 34,
```

Builder classes for the agent task types should follow once the agent task API stabilizes.

Related: Java SDK [#135](https://github.com/conductor-oss/conductor-java-sdk/issues/135), JavaScript SDK [#140](https://github.com/conductor-oss/javascript-sdk/issues/140), Go SDK [#265](https://github.com/conductor-oss/go-sdk/issues/265)

Open Conductor/Client/Models/WorkflowTask.cs and inspect WorkflowTaskTypeEnum, whose current values end at WAITFORWEBHOOK = 30. Add the four specified enum members with their EnumMember values and numeric assignments, then verify that workflow definitions containing these task types serialize and deserialize to the expected enum values; builder classes are outside this issue's scope.

Written by the indexing model from the issue text.