Error from provider (Console Go): Unsupported custom tool 'exec' — only 'apply_patch' is supported (deepseek-v4-flash)

**提交人**: RipppppX
**客户端版本**: 0.1.45

---

## 现象
对话过程中模型请求持续失败，返回错误：

```json
{"model":"deepseek-v4-flash","error":{"param":null,"code":"invalid_request_error","type":"invalid_request_error","message":"Error from provider (Console Go): Upstream request failed: [invalid_request_error] Unsupported custom tool: 'exec'. Only 'apply_patch' is supported."}}
```

含义：模型 deepseek-v4-flash（上游 Console Go）被允许调用的自定义工具集与上游支持的工具不一致——模型试图调用 `exec`，但上游只支持 `apply_patch`，导致请求被拒。

## 复现步骤
在对话中持续发消息（多轮对话）即出现；具体触发轮数/触发条件用户未知。

## 期望行为
对话正常继续，模型正常响应，不应因工具集不匹配而请求失败。

## 实际行为
多轮对话后请求稳定失败，返回上述错误。

## 复现频率
每次均稳定复现。

## 已尝试
- 重试：无效
- 切换 Agent：无效
---
**版本区域**: CN
**OS**: win32 x64 (10.0.26200)
**界面语言**: zh-CN

No source file or test is named. Start by tracing the provider custom-tool handling for deepseek-v4-flash and compare the requested exec tool with the supported apply_patch tool. Done means multi-turn conversations no longer fail with the unsupported custom-tool error.

Written by the indexing model from the issue text.