feat(#130): add VCS routing in cmd/review-bot via --vcs-type flag

- Add vcs_client.go with vcsClient interface, giteaClientVCSAdapter, githubClientVCSAdapter
- Add giteaExtendedClient interface for Gitea-specific operations (supersede, resolve, etc.)
- Add --vcs-type flag (gitea|github, default: gitea) with VCS_TYPE env var support
- Replace direct giteaClient usage with vcsClient interface in main.go
- Add verdictToVCSEvent() to map LLM verdict to vcs.ReviewEvent
- Gitea adapter translates vcs.ReviewEvent back to Gitea API format (APPROVE->APPROVED)
- Guard Gitea-specific ops (RequestReviewer, supersede, resolve) with type assertion
- Guard fetchPatterns GetAllFilesInPath with Gitea-only type assertion
- Replace reviewClientAdapter (giteaClientAdapter) for review.GiteaClient interface
- Update main_test.go to use reviewInfo/commitStatusInfo instead of gitea types

vcs/types.go

@@ -48,6 +48,12 @@ type ReviewRequest struct {
 	// Event is the review verdict.
 	Event ReviewEvent
 
+	// CommitID is the commit SHA that this review targets.
+	// When non-empty, the review is anchored to this commit.
+	// For GitHub, this is passed as commit_id in the review request.
+	// For Gitea, this is passed as the commitID parameter to PostReview.
+	CommitID string
+
 	// Comments are optional inline file-level comments.
 	Comments []ReviewComment
 }