Fix unknown diagram error in Mermaid rendering

[Copilot]

Fixes the "Unknown diagram error" that occurs when using png_url or svg_url output types with mermaid.ink.

Root Cause

createMermaidInkUrl was compressing the raw mermaid syntax string directly, but mermaid.ink's pako: endpoint expects the payload to be a JSON object in the format {"code": "<mermaid>", "mermaid": {"theme": "..."}} — the same format used by the Mermaid Live Editor.

Changes Made

• src/utils/mermaidUrl.ts: Updated createMermaidInkUrl to wrap the mermaid code in the required JSON payload {code, mermaid: {theme}} before deflating and base64url-encoding it. Added a theme parameter to the function signature.
• src/server.ts: Pass the user-selected theme (with "default" fallback) through to createMermaidInkUrl.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Unknown diagram error</issue_title>
<issue_description>Hi,

I tried running your MCP server in VSCode using the sample Mermaid snippet from Mermaid Live Editor, but when I click the generated link, I get an “Unknown diagram error”.

Could you advise what I might be doing wrong?

Thanks!

Here’s what I used:

flowchart TD
    A[Christmas] -->|Get money| B(Go shopping)
    B --> C{Let me think}
    C -->|One| D[Laptop]
    C -->|Two| E[iPhone]
    C -->|Three| F[fa:fa-car Car]

Input

{
  "mermaid": "flowchart TD\n    A[Christmas] -->|Get money| B(Go shopping)\n    B --> C{Let me think}\n    C -->|One| D[Laptop]\n    C -->|Two| E[iPhone]\n    C -->|Three| F[fa:fa-car Car]",
  "outputType": "png_url"
}

Output Link:
https://mermaid.ink/img/pako:eNpVy7EKwjAURuHdp_hHHfoCDoJNtUuhDt1Chku5NUGbG5JAEeO7SzvpfL4zPWUZLcWModkBwFkrG13KMyWDqjqVljNm8fwqqPetIFkJwfn7YeP1aqDe3aoY2Tr_-GxFbXfvuaDRHYUswfyEYZGCi3Y3K57_go3MBVc90XGiaqQIRdF8ATbHM0c

Screenshot:

</issue_description>

<agent_instructions>尝试帮我解决一下。</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Unknown diagram error #32

---

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[hustcc]

@copilot 继续

[Copilot]

@copilot 继续

Fixed in a1e9325.

Root cause: createMermaidInkUrl was deflating the raw mermaid string, but mermaid.ink's pako: endpoint expects a JSON payload {"code": "...", "mermaid": {"theme": "..."}}.

Changes:

• src/utils/mermaidUrl.ts: wrap mermaid code in the JSON object before deflating/base64url-encoding
• src/server.ts: pass the selected theme (with "default" fallback) into createMermaidInkUrl

[hustcc]

@copilot 给我一个测试链接，我验收看看。

[Copilot]

@copilot 给我一个测试链接，我验收看看。

使用 issue 中相同的 flowchart 示例生成的测试链接：

PNG: https://mermaid.ink/img/pako:eNpVz70OgjAUhuFbOemkidwAg4kUZSHRga0ynMCpbaQ_KTXEUO7dIIvO7_MN38w61xPLmRzc1CkMEZrybgEAToKroMdocGwhy46pogjGWXonKHaVg1E577V97DdfrAj4XK-MICptn8uW-Hd_tZSgFDX66Hz7W5rJJTgLfVPO0n9RgSjBRUjMJWYdBuAYWnZghoJB3bN8ZlGRWT_0JPE1RLYsH9QZRJc

SVG: https://mermaid.ink/svg/pako:eNpVz70OgjAUhuFbOemkidwAg4kUZSHRga0ynMCpbaQ_KTXEUO7dIIvO7_MN38w61xPLmRzc1CkMEZrybgEAToKroMdocGwhy46pogjGWXonKHaVg1E577V97DdfrAj4XK-MICptn8uW-Hd_tZSgFDX66Hz7W5rJJTgLfVPO0n9RgSjBRUjMJWYdBuAYWnZghoJB3bN8ZlGRWT_0JPE1RLYsH9QZRJc

这两个链接使用的是修复后的 JSON 格式 {"code": "...", "mermaid": {"theme": "default"}} 编码，对应 issue 中的 flowchart 图表。