Muse Spark fix for DeepSeek Harness

# Muse Spark via OpenCode Go in DeepSeek Harness (DSH)

> 让 `muse-spark-1.2-contributor`（OpenCode Zen Go 网关）在 DeepSeek Harness（`deepseek-harness` / `pi-ai`）里正确工作：首轮出内容 + 多轮 thinking 回传不报错。
>
> Make `muse-spark-1.2-contributor` (the OpenCode Zen Go gateway model) work correctly in DeepSeek Harness (`deepseek-harness` / `pi-ai`): first-turn output plus lossless multi-turn thinking replay.

> **免责声明 / Disclaimer**：本仓库是个人技术分享，**非** DeepSeek / opencode 官方项目，与 `deepseek-ai`、`sst/opencode`、`opencode.ai` 均无关联。文中涉及的协议与代码分析基于公开接口，仅用于学习与自用。
> This is a personal tech-sharing repo. It is **not** an official DeepSeek or opencode project and is unrelated to `deepseek-ai`, `sst/opencode`, or `opencode.ai`. Protocol/code analysis herein is based on public interfaces, for learning and personal use only.

| 项目 | 值 |
| --- | --- |
| 模型 | `muse-spark-1.2-contributor` (Muse Spark 1.2 Contributor) |
| 网关 | OpenCode Zen Go — `https://opencode.ai/zen/go/v1` |
| 协议（正确） | **OpenAI Responses API** (`openai-responses`) |
| 宿主 | DeepSeek Harness (`deepseek-harness`), LLM 适配层 `@deepseek-ai/dsh-llm-pi-ai` → `@earendil-works/pi-ai` |
| 状态 | ✅ 已验证：多轮 + thinking 回传 + 工具调用 + **图片输入** 正常 |

---

## 一、问题现象 / Symptoms

在 `~/.dsh/settings.yaml` 里用 `muse-spark-1.2-contributor`，无论怎么配都会遇到下列错误之一：

| 配置的协议 | 现象 |
| --- | --- |
| `openai-completions` | `Stream ended without finish_reason`（流被网关截断，`message.content` 恒为空） |
| `anthropic-messages` | `model returned a completed response with no content`（非流式空回复） |
| `openai-responses` + 错误的 assistant 补丁 | `input[5] did not match any supported type`（发了 responses 不认识的输入项） |
| `openai-responses`（原始）多轮 | `reasoning_content in the thinking mode must be passed back to the API` |

而 **在 opencode 官方客户端里，Muse 完全正常**。

---

## 二、为什么 opencode 能用 / Why it works in opencode

opencode 的模型目录来自 `https://models.opencode.ai/api.json`（本地缓存在 `~/.cache/opencode/models.json`）。其中：

```jsonc
// provider "opencode-go"
{
  "id": "opencode-go",
  "npm": "@ai-sdk/openai-compatible",
  "api": "https://opencode.ai/zen/go/v1"
}
// model "muse-spark-1.2-contributor"
{
  "provider": { "npm": "@ai-sdk/openai" },   // ← 关键：模型级覆盖为 OpenAI Responses SDK
  "reasoning_options": [
    { "type": "effort", "values": ["minimal", "low", "medium", "high", "xhigh"] }
  ],
  "limit": { "context": 1048576, "output": 131072 }
}
```

**Muse 只认 OpenAI Responses 协议**（模型级 `@ai-sdk/openai`），不是 Chat Completions、也不是