Creating a new Agent toasts "Agent config version not found" for a missing build-draft

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### Dify version

1.16.1

### Cloud or Self Hosted

Self Hosted (Docker)

### Steps to reproduce

1. Create a new Agent.
2. Open the Agent configure page (it defaults to Build mode).
3. The page immediately GETs `/console/api/agent/{id}/build-draft`.

Screenshot of the toast:

### ✔️ Expected Behavior

A missing build-draft after create is an empty state. Stay on the normal draft and do not toast.

### ❌ Actual Behavior

The API returns 404 `Agent config version not found` because the new agent has no DEBUG_BUILD row. The UI toasts that 404 as a version error (Flask-RESTX also appends "did you mean ...").