API docs parity: Node.js / TypeScript

## Node.js / TypeScript API Docs

**Parent epic:** #1653

**Doc format:** [TSDoc](https://tsdoc.org/) / [TypeDoc](https://typedoc.org/) comments (`/** ... */` with `@param`, `@returns`, etc.). TypeDoc generates HTML from these.

**Culture:** Weaker than Java. npm does **not** require a docs artifact to publish. Many packages ship only a README + inline types (the `.d.ts` files *are* the docs for many TS consumers via IDE hover). Publishing standalone API docs is opt-in.

**Hosting analogues:**

| Service | How it works |
|---------|-------------|
| [typedoc.org](https://typedoc.org/) | Generator, not host |
| [tsdocs.dev](https://tsdocs.dev/) | Closest to javadoc.io — auto-generates docs from any npm package's types on demand |
| GitHub Pages / custom | Many projects self-host (e.g. `docs/` folder or CI-published site) |

**Key difference from Java:** No registry-mandated doc artifact. `tsdocs.dev` synthesizes docs from published `.d.ts` type declarations rather than a pre-built doc jar.

### Additional research: tsdocs.dev fragility

As of 2026-06-13, tsdocs.dev returns **502 Bad Gateway** across the board — both the homepage and package-specific URLs (e.g. `https://tsdocs.dev/docs/@github/copilot-sdk`). The service is completely down, not just a homepage glitch.

This reinforces the fragility of the TypeScript ecosystem's doc hosting: tsdocs.dev is a volunteer-run third-party project, not backed by npm or Microsoft. It has had reliability issues before. There is no npm Inc. or TypeScript team commitment keeping it running — unlike docs.rs (Rust team) or pkg.go.dev (Go team), which are first-party infrastructure with SLAs.

In practice, for the `@github/copilot-sdk` npm package, the realistic API-docs options are:

1. **Self-host TypeDoc output** (e.g., GitHub Pages from CI) — most reliable
2. **Rely on `.d.ts` hover docs in IDEs** — what most TS consumers actually use day-to-day
3. **tsdocs.dev** — when it's up, which apparently is not guaranteed

**As a Java Champion perspective:** Java's Maven Central mandate for javadoc jars means API docs are a first-class, always-available artifact. This is particularly important in an era where AI is writing code — maintainability depends on discoverable, reliably-hosted documentation. The TypeScript ecosystem lacks this guarantee, making self-hosted docs a necessity rather than optional.

Bắt đầu bằng cách đọc epic cha #1653 và phần thảo luận của issue về TSDoc, TypeDoc, tsdocs.dev, GitHub Pages và các tệp .d.ts đã được publish. Issue không nêu tệp nào trong repository, test hay điểm bắt đầu của việc triển khai; công việc chỉ hoàn tất khi cách tiếp cận tài liệu API của project và deliverable được quyết định rõ ràng.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.