[Bug]: Failed to operate on deepseek chat

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### Description

The first 2 requests was success, but the latest request failed. I am running OpenCLI in wsl(6.18.33.2-microsoft-standard-WSL2), the host OS is windows 11, chrome is on Windows.

### Steps to Reproduce

1. Run `opencli deepseek ask "hello" --new`
2. The first 2 runs of the command was successful
4. See error

### Expected Behavior

Should not have error

### OpenCLI Version

1.8.7

### Node.js Version

22.x

### Operating System

Windows

### Logs / Screenshots

```shell
->opencli deepseek ask "explain quicksort in 3 sentences"

deepseek/ask
┌──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ Response │
├──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
│ Quicksort picks a "pivot" element from the array and partitions the other elements into two groups: those less than the pivot and those greater than it. It then recursively applies the same process to each group until every subarray has one or zero elements. On average it runs in O(n log n) time and sorts in place, though its worst case is O(n²) when partitions are very unbalanced. │
└──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
1 items · 9.2s · deepseek/ask
->opencli deepseek ask "impl splay tree in rust 2024"

deepseek/ask

^C
->opencli deepseek ask "impl splay tree in rust 2024" --think --new
ok: false
error:
code: COMMAND_EXEC
message: Could not switch to instant model
exitCode: 1
```

Start by reproducing the `opencli deepseek ask` command with `--think --new` after several requests, then trace the command entry point handling the reported instant-model switch. Done means the request completes without `COMMAND_EXEC` or the “Could not switch to instant model” error in the stated WSL and Windows environment.

Written by the indexing model from the issue text.