fix(cmd,github): address review feedback on PR #106

- Replace panic() with fmt.Fprintf+os.Exit(1) in provider switch default
  (repo convention: never panic)
- Remove spurious 'event' field from DismissReview payload (GitHub dismiss
  endpoint only documents 'message')
- Change translateReviewEvent default to return 'COMMENT' as canonical
  fallback instead of passing unknown events through to GitHub API
- Refactor supersedeOldReviews to use explicit switch/case with default
  error for exhaustiveness

github/reviews.go

@@ -42,7 +42,6 @@ type reviewCommentCreate struct {
 // dismissReviewRequest is the GitHub API request body for dismissing a review.
 type dismissReviewRequest struct {
 	Message string `json:"message"`
-	Event   string `json:"event"`
 }
 
 // userResponse is the GitHub API response for the authenticated user.
@@ -60,7 +59,7 @@ func translateReviewEvent(event vcs.ReviewEvent) string {
 	case vcs.ReviewEventComment:
 		return "COMMENT"
 	default:
-		return string(event)
+		return "COMMENT"
 	}
 }
 
@@ -161,7 +160,6 @@ func (c *Client) DismissReview(ctx context.Context, owner, repo string, number i
 
 	payload := dismissReviewRequest{
 		Message: message,
-		Event:   "DISMISS",
 	}
 
 	_, err := c.doJSONRequest(ctx, http.MethodPut, reqURL, payload)