refactor(capture): CloseIssue carries a closing comment (#52)

#52's IssueTracker spec is CloseIssue(repo, number, comment). Refine the
#51 port signature to match and have the service pass the ticket body as
the closing comment (empty ⇒ close only). Keeps the close-with-comment
flow first-class rather than forcing two separate ticket items.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ingestion/internal/capture/service.go

@@ -222,7 +222,7 @@ func (s *Service) persistTicket(ctx context.Context, tk Ticket) (TicketResult, e
 	case "create":
 		ref, err = s.issues.CreateIssue(ctx, tk.Repo, tk.Title, tk.Body)
 	case "close":
-		ref, err = s.issues.CloseIssue(ctx, tk.Repo, tk.Number)
+		ref, err = s.issues.CloseIssue(ctx, tk.Repo, tk.Number, tk.Body)
 	case "comment":
 		ref, err = s.issues.CommentIssue(ctx, tk.Repo, tk.Number, tk.Body)
 	}