feat: Cindy创建Worker只有「框架 + 模型 + 推理强度」，指定不了供应商。

### 使用场景 / Use case

导致多个中转站的同类型Claude模型无法自动调用切换，

### 当前问题 / Current limitation

中转站很不稳定，需要有备选的同模型的Worker。

### 期望方案 / Proposed solution

Worker创建工具可以「框架 + 模型供应商 + 模型 + 推理强度」

### 已考虑的替代方案 / Alternatives considered

_No response_

Start by locating the Worker creation flow and the existing inputs for framework, model, and reasoning strength. Trace how a Worker selects a model, then verify that a model provider can also be selected so equivalent models from different relay services can be distinguished and used as alternatives.

Written by the indexing model from the issue text.