addTaskComment posts one comment and can pin it to the top of task activity.
automations/comment-on-asana-task.automation.ts
taskId is required. Provide exactly one of non-empty text or htmlText; htmlText must use Asana-supported rich-text HTML. Optional isPinned controls pinning, and account defaults to the project binding.
Returns the created AsanaStory. Keep its id for updates or deletion.