API docs parity: .NET

## .NET API Docs

**Parent epic:** #1653

**Doc format:** [XML documentation comments](https://learn.microsoft.com/dotnet/csharp/language-reference/xmldoc/) (`/// `, ``, ``, etc.). The compiler emits a `.xml` file alongside the assembly.

**Culture:** **Strong and enforced.** NuGet packages conventionally include the XML doc file in the package (IDE IntelliSense reads it). Microsoft's own libraries always ship it. Roslyn analyzers can warn on missing docs.

**Hosting analogues:**

| Service | How it works |
|---------|-------------|
| ~~[fuget.org](https://www.fuget.org/)~~ | ⚠️ **Defunct** — DNS no longer resolves as of 2026-06-13. Was the closest analogue to javadoc.io for NuGet packages |
| [NuGet package page](https://www.nuget.org/) | Shows README, not full API surface |
| [DocFX](https://dotnet.github.io/docfx/) | Microsoft's Sphinx-equivalent generator; many projects self-host output on GitHub Pages |

> **Note on fuget.org:** fuget.org was the only third-party service that automatically rendered API docs from NuGet packages (analogous to javadoc.io). As of 2026-06-13 it is completely offline — DNS does not resolve. This means there is **no automatic, zero-config API docs host** for .NET packages. Self-hosted DocFX output (e.g. GitHub Pages from CI) is the only viable option.

**Key difference from Java:** The XML doc file ships *inside* the `.nupkg` (analogous to javadoc jar living in Maven Central), so IDEs can consume it without separate publication. But NuGet doesn't *mandate* it the way Maven Central does, and with fuget.org gone, there is no hosted equivalent to javadoc.io for .NET.

首先检查此 parity issue 涉及的 .NET API 表面，以及 repository 现有的文档编写方式。该 issue 规定了 XML 文档注释，并讨论了 NuGet 打包和 DocFX，但没有指定文件、测试或确切的 API 范围。要视为完成，需要确定一致认可的 .NET 文档范围，并记录生成或发布 API 参考的方法。

由索引模型根据 Issue 内容生成。