fix(github): clarify GetTimelineReviewCommentIDForReview supersede limitations

The supersede path calls GetTimelineReviewCommentIDForReview then EditComment.
On GitHub, EditComment targets /pulls/comments/{id} (for inline review comments),
but review bodies are not inline comments. The PATCH will return 404 and be
logged as a warning. The review itself posts correctly regardless.
This is a known limitation pending a future fix via the reviews PATCH endpoint.

github/methods.go

@@ -529,9 +529,12 @@ func (c *Client) ResolveComment(_ context.Context, _, _ string, _ int64) error {
 
 // GetTimelineReviewCommentIDForReview finds the timeline comment ID for a review.
 // GitHub doesn't have a direct timeline event endpoint for reviews the way Gitea does.
-// This is primarily used by the cleanup path (EditComment + resolve). On GitHub,
-// we return the review ID itself since GitHub PR review IDs are stable.
-// Returns the reviewID unchanged for compatibility.
+// This is primarily used by the supersede path (EditComment + ResolveComment). On GitHub,
+// we return the review ID itself. Note that EditComment on GitHub uses the
+// /pulls/comments/{id} endpoint (for inline review comments), which does not
+// apply to review bodies — the supersede EditComment call will 404 and be
+// logged as a warning. This is a known limitation; the review is still posted
+// correctly regardless.
 func (c *Client) GetTimelineReviewCommentIDForReview(_ context.Context, _, _ string, _ int, reviewID int64) (int64, error) {
 	return reviewID, nil
 }