Add Go GitHub API parity foundation (#120)

* Add Go GitHub API parity foundation

- Adds a dependency-free native GitHub REST and OAuth service covering users, orgs, repos, issues, comments, pull requests, git data, rate limit, meta, and seed data.

- Mounts GitHub in the native runtime and CLI seed parser while keeping npm distribution and TypeScript packages in place.

- Includes GitHub in Vercel Go Function preview defaults and updates docs, skills, help text, and focused tests.

* Fix native GitHub parity regressions

* Fix native GitHub parity review issues

* Fix native GitHub review issues

* Fix native GitHub permission and PR parity

* Fix native GitHub access regressions

* Fix native GitHub parity regressions

* Fix native GitHub review regressions

* Fix native GitHub issue parity regressions

* Fix native GitHub parity regressions

* Fix native GitHub parity review issues

* Fix native GitHub PR merge regressions

* Fix native GitHub issue parity gaps

* Fix GitHub collaborator write permissions