Add three new services completing the final service layer:
- WikiService: CRUD operations for repository wiki pages
- MiscService: markdown rendering, licence/gitignore templates, nodeinfo, version
- CommitService: commit statuses (list, create, combined) and git notes
- PostRaw method on Client for endpoints returning raw text (e.g. /markdown)
- Remove services_stub.go (all stubs now replaced with real implementations)
- Wire Commits field into Forge struct
Co-Authored-By: Virgil <virgil@lethean.io>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
