fix: address review findings (escalation, marshal error, redundant check)

1. First-run escalation regression (MAJOR): Add post-posting escalation
   fallback. After posting APPROVED on first run, check if a sibling
   from the same user has REQUEST_CHANGES — if so, mark ours as
   superseded and re-post as REQUEST_CHANGES.

2. json.Marshal error handling (MINOR): Return error from EditComment
   instead of ignoring it with blank identifier.

3. Redundant condition (NIT): Remove dead assignment in reviewUnchanged
   where existingEvent was assigned from r.State then compared to itself.

cmd/review-bot/main.go

@@ -316,11 +316,35 @@ func main() {
 
 	// POST new review (first run, or state transition fallthrough)
 	log.Printf("Posting review (event=%s)...", event)
-	_, err = giteaClient.PostReview(ctx, owner, repoName, prNumber, event, reviewBody, inlineComments)
+	posted, err := giteaClient.PostReview(ctx, owner, repoName, prNumber, event, reviewBody, inlineComments)
 	if err != nil {
 		log.Fatalf("Failed to post review: %v", err)
 	}
-	log.Printf("Review posted successfully")
+	log.Printf("Review posted (id=%d, user=%s)", posted.ID, posted.User.Login)
+
+	// Post-posting escalation: if we just posted APPROVED but a sibling
+	// from the same user has REQUEST_CHANGES, mark ours as superseded and
+	// re-post as REQUEST_CHANGES. This handles the first-run case where
+	// we don't know our login until after posting.
+	if event == "APPROVED" && *updateExisting && *reviewerName != "" {
+		reviews, err := giteaClient.ListReviews(ctx, owner, repoName, prNumber)
+		if err == nil && shouldEscalate(reviews, posted.ID, posted.User.Login, sentinel) {
+			log.Printf("Post-posting escalation: sibling has REQUEST_CHANGES")
+			// Mark our just-posted review as superseded
+			commentID, err := giteaClient.GetTimelineReviewCommentID(ctx, owner, repoName, prNumber, sentinel)
+			if err == nil {
+				supersededBody := fmt.Sprintf("~~*This review has been superseded by a newer review below.*~~\n\n%s", sentinel)
+				giteaClient.EditComment(ctx, owner, repoName, commentID, supersededBody)
+			}
+			// Re-post as REQUEST_CHANGES
+			_, err = giteaClient.PostReview(ctx, owner, repoName, prNumber, "REQUEST_CHANGES", reviewBody, inlineComments)
+			if err != nil {
+				log.Printf("Warning: could not re-post as REQUEST_CHANGES: %v", err)
+			} else {
+				log.Printf("Review escalated to REQUEST_CHANGES")
+			}
+		}
+	}
 }
 
 // fetchFileContext fetches the full content of modified files from the PR branch.
@@ -508,9 +532,7 @@ func reviewUnchanged(reviews []gitea.Review, newBody, newEvent, sentinel string)
 		if !strings.Contains(r.Body, sentinel) {
 			continue
 		}
-		// Compare state (map APPROVED back from Gitea's representation)
-		existingEvent := r.State
-		if existingEvent == r.State && existingEvent == newEvent && r.Body == newBody {
+		if r.State == newEvent && r.Body == newBody {
 			return true
 		}
 	}

gitea/client.go

@@ -407,7 +407,10 @@ func (c *Client) EditComment(ctx context.Context, owner, repo string, commentID
 	payload := struct {
 		Body string `json:"body"`
 	}{Body: newBody}
-	data, _ := json.Marshal(payload)
+	data, err := json.Marshal(payload)
+	if err != nil {
+		return fmt.Errorf("marshal edit payload: %w", err)
+	}
 
 	req, err := http.NewRequestWithContext(ctx, http.MethodPatch, reqURL, bytes.NewReader(data))
 	if err != nil {