- Add --provider flag (gitea|github) for VCS backend selection
- Add --base-url flag for GitHub API endpoint configuration
- Rename --gitea-url to --vcs-url with backward-compatible alias
- Replace direct gitea.Client usage with vcs.Client interface
- Create vcs.Client via factory switch based on --provider value
- Implement Reviewer + Identity interfaces on github.Client
- Add verdictToEvent() using canonical vcs.ReviewEvent types
- Remove review.GiteaEvent() (replaced by verdictToEvent)
- GitHub supersede uses DismissReview; Gitea keeps EditComment flow
- Add VCS_PROVIDER, VCS_BASE_URL, VCS_URL env var support
Closes#82
claw