[Bug] Model Qwen3.5 9b does not run with WebGPU

### Describe the issue

```
natke@timmy % foundry run qwen3.5-9b
● error: IPC error 'op_handler_failed': Error loading model qwen3.5-9b-generic-gpu:3: Error:
Microsoft.ML.OnnxRuntimeGenAI.OnnxRuntimeGenAIException: This is an invalid model. Error:
Duplicate definition of name (image_grid_thw_CUDAExecutionProvider).
at Microsoft.ML.OnnxRuntimeGenAI.Result.VerifySuccess(IntPtr) + 0x48
at Microsoft.ML.OnnxRuntimeGenAI.Model..ctor(Config) + 0x20
at Microsoft.Neutron.OpenAI.Provider.OnnxLoadedModel..ctor(String, Config, GenAIConfig,
InferenceModel, OnnxEP) + 0x64
at Microsoft.AI.Foundry.Local.ModelManager.d__9.MoveNext() + 0xb78
--- End of stack trace from previous location ---
at
Microsoft.AI.Foundry.Local.NativeInterop.<>c__DisplayClass10_0.<b__5>d.Move
Next() + 0x84
--- End of stack trace from previous location ---
at Microsoft.AI.Foundry.Local.NativeInterop.d__9.MoveNext() + 0xa8
Hint: Try 'foundry server stop' then 'foundry server start'.
```

Foundry Local version: `0.10.3`
O/S: macOS

### To reproduce

```
brew install foundrylocal
foundry run qwen3.5-9b
```

### Urgency

_No response_

### Platform and architecture

Windows X64

### OS Version

macOS 15.7.9

### Installation type

Released package/binary

### Foundry Local version

0.10.3

### API or surface area

CLI

### Hardware acceleration/backend

WebGPU/CUDA

### Backend/runtime version

_No response_

Start by reproducing `foundry run qwen3.5-9b` on macOS 15.7.9 with Foundry Local 0.10.3, then trace the model-loading path shown in the error. Investigate the duplicate `image_grid_thw_CUDAExecutionProvider` definition and verify that the command loads the model without the invalid-model error.

Written by the indexing model from the issue text.