[Feature] Support path parameters in AgentApp endpoint_path

## Problem Description
Currently, when using the `endpoint_path` specified in `AgentApp`, it does not support variables/placeholders. Could this feature be supported? For example:

```python
endpoint_path = "/agent/{agent_id}/chat"
```

Then, in the `query_func` method, we should be able to retrieve this agent_id parameter.

## Proposed Solution
[Clear description of what you want to happen]

## Affected Component(s)
- [x] Engine
- [ ] Sandbox
- [ ] Common
- [ ] Tools
- [ ] Documentation
- [ ] Other: ___________