fix(review): address inline review feedback on PR #106

- Reword misleading 'Fall through' comment to 'Continue to' in
  supersedeOldReviews (comment #18704)
- Add shared-pointer explanation comment for --gitea-url alias
  registration (comment #18703)
- Add comment clarifying CommitID same-commit expectation in
  PostReview (comment #18705)
- Rename 'hidden alias' to 'backward-compatible alias' in flag
  comment (comment #18708)

github/reviews.go

@@ -80,7 +80,8 @@ func (c *Client) PostReview(ctx context.Context, owner, repo string, number int,
 			Body:     comment.Body,
 		}
 		payload.Comments = append(payload.Comments, rc)
-		// Use CommitID from the first comment that has one
+		// Use CommitID from the first comment that has one.
+		// All comments in a single review are expected to reference the same commit.
 		if payload.CommitID == "" && comment.CommitID != "" {
 			payload.CommitID = comment.CommitID
 		}