TaskType enum missing AGENT, GET_AGENT_CARD, CANCEL_AGENT, PULL_WORKFLOW_MESSAGES

## Summary

Four task types added to the Conductor server in 3.32.0-rc.9 (conductor-oss/conductor PR #1288)
are absent from the `TaskType` enum in `src/open-api/types.ts`. Users cannot reference
these types via the SDK without using raw strings.

## Server baseline

Conductor **3.32.0-rc.9**

## Missing values

Server `TaskType.java` has:
```java
PULL_WORKFLOW_MESSAGES,
AGENT,
GET_AGENT_CARD,
CANCEL_AGENT;
```

All four are absent from the SDK `TaskType` enum.

## Evidence

**Static:** `TaskType` enum in `types.ts` ends at `LIST_MCP_TOOLS`. All four values absent.

**Live (2026-07-16):** A raw task with `"type": "AGENT"` was registered against
Conductor OSS 3.32.0-rc.9. Server accepted the definition — the gap is SDK-only.

## Proposed fix

Add to `TaskType` enum in `src/open-api/types.ts`:
```typescript
PULL_WORKFLOW_MESSAGES = "PULL_WORKFLOW_MESSAGES",
AGENT = "AGENT",
GET_AGENT_CARD = "GET_AGENT_CARD",
CANCEL_AGENT = "CANCEL_AGENT",
```

Builder functions for AGENT, GET_AGENT_CARD, and CANCEL_AGENT should follow once the
agent task API is stable.

## Related

Discovered during systematic SDK audit against Conductor OSS 3.32.0-rc.9.
Server PR: conductor-oss/conductor#1288
Same gap in Java SDK (conductor-oss/java-sdk#135) and Python SDK (conductor-oss/python-sdk#431).

Open src/open-api/types.ts and inspect the TaskType enum, which currently ends at LIST_MCP_TOOLS. Add the four server values listed in the issue, then verify the TypeScript SDK builds and that all four names can be referenced without raw strings.

Written by the indexing model from the issue text.