Documentation site (TypeDoc + custom layout)

[pathosDev]

GitHub Pages deploy of TypeDoc-generated API reference plus the README sections rendered as standalone pages. Adds a 'Docs' link to the README and reduces README length.

[pathosDev]

Done — delivered as a Starlight site rather than the "TypeDoc + custom layout" originally sketched, but every ask is met. Checked one by one:

• GitHub Pages deploy — .github/workflows/docs.yml.
• TypeDoc-generated API reference — 319 generated pages under docs/src/content/docs/api/ (classes, interfaces, functions, enumerations, type-aliases, variables), published at actor-ts.dev/api/.
• README sections rendered as standalone pages — quickstart, why-actors, migration, DevTools and the rest of the site.
• "Docs" link in the README + a shorter README — README.md:245-259 links the site, the quickstart, why-actors, the migration guide, DevTools and the API reference; the README is down to 309 lines.

The site also carries a full German mirror, which was not in scope here.

No residual scope, so nothing to re-file.