ZFS Boot Mirrors on Proxmox 8 for the Homelab - Part 4

A real execution of the Part 3 planned-migration procedure against a live node with both ZFS boot mirror drives degraded. Covers the SMART trigger, a confirmed UEFI dead end on this hardware, gaps in the original checklist (SAN network, Ceph mon/mgr recreation, USB SMART quirks), a hostid mistake that broke the next boot, a live OSD failure caused by the USB gap, and full verification.