append_task_note and workspace notes for agents

append_task_note adds one dated entry to the end of a task’s notes, headed with the time, the workspace member and the agent’s own label, without reading and rewriting the whole note. Agents appending to the same task at once all keep their entries; none is lost to a last write.

Workspace notes give agents and people one shared place for what is not a task: list_notes, get_note, create_note, append_note and update_note.