feat: TypeDoc API docs + GitHub Pages

[OneStepAt4time]

Doc Pipeline — TypeDoc + GitHub Pages

Parent: #440 (Roadmap) — also tracked as doc supply chain (#370)
Milestone: M3 — Reference Implementation

This is a duplicate tracking of #370 under the correct milestone. See #370 for full spec.

Summary

• Install and configure TypeDoc
• Add TSDoc comments to all public API methods
• Deploy to GitHub Pages
• npm run docs generates docs/api/

⚠️ Use plan mode + brainstorming skill before writing any code.

[OneStepAt4time]

Closing as completed by merged PR #1071, which added TypeDoc generation and GitHub Pages publishing workflow for API docs.