feat(ui/chat): remove redundant attachment URL line

Attachment filenames are now OSC 8 hyperlinks (clickable in supported
terminals), so the separate full-URL line below each filename is no
longer needed. The show_attachment_links config toggle is now unused.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/ui/chat/messages_list.go

@@ -501,13 +501,7 @@ func (ml *messagesList) drawDefaultMessage(builder *tview.LineBuilder, message d
 	attachmentStyle := ui.MergeStyle(baseStyle, ml.cfg.Theme.MessagesList.AttachmentStyle.Style)
 	for _, a := range message.Attachments {
 		builder.NewLine()
-		if ml.cfg.ShowAttachmentLinks {
-			builder.Write(a.Filename+":", attachmentStyle)
-			builder.NewLine()
-			builder.Write(a.URL, attachmentStyle.Url(a.URL))
-		} else {
-			builder.Write(a.Filename, attachmentStyle)
-		}
+		builder.Write(a.Filename, attachmentStyle.Url(a.URL))
 	}
 
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