Restore guiRootDisk1/guiRootDisk2, lost in a merge conflict on main

These were dropped from variables.nix by a stash/merge conflict
resolution on main (commit fb6ee27) that kept the new wifiSsid value
but discarded the two disk-path variables entirely, leaving unresolved
`<<<<<<< Updated upstream` markers in an intermediate commit before
being cleaned up. modules/disko/baremetal.nix references both directly
with no fallback, so baremetal-gui has been failing to evaluate on main
since that commit ("attribute 'guiRootDisk1' missing") -- confirmed by
cloning main fresh and evaluating config.disko.devices.disk.disk1.device
directly.

This commit is rebased onto latest main (through "updated secrets",
which registered baremetal-gui's real sops recipient) rather than the
older base this branch started from.

variables.nix

@@ -45,12 +45,20 @@
   # the installer image's nixos/root users.
   adminSshKey = "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABgQCq/Q5LvIXlZwO2kdeAN5nLGZ59nZB7JHYMEszHxmNtGMzv1lM31jiPNsr0z2EKVZhE7OOfa2IF9rhWYD7JUA9G0yzdZ4WTXFNGVVOJoOVH6vAF3XCxoVilOEwTc7h2Wiy+rzd0B28/3spffzQQWJhY6GRQVa8j+6xAGF60Fcvl1vLosYT9Bn2ZbK4TCWOwAn2jqXIieGpZdn/UNZbGOeKRiCvhktDfMAzuQzN/9jMu/oF4pkPn2X1UrsQdNlvp0Ci8md612MozIpncQJyAF1ADhunr3sMx0isUXiqD29R5DS4TftpekqLNLak+zcxFa8N7DcRNp3DcKfJvyTkwQrR4r+b7lFLYOLHLagSso9CzeW/paAS2q9I5SBm/2DtE1diLLg2jZikYcstsu/G5RgvbzbKqjiaMwTdXC3AMvDxQrs7U5pDRZFzoofG3cpODbTm+uy3m0kP70z0M1K45UbDG0p+itnTu9x40JbQEgefbx38AItNvAIx1A8HO4I1VX28= wayne@stream";
 
-  # Prestaged wifi credentials for the gui host's NetworkManager profile
-  # (modules/networking/wifi.nix). Leave blank until the bare-metal
-  # hardware profile is wired up — an empty ssid disables the profile
-  # rather than creating a broken empty one.
+  # Prestaged wifi SSID for the gui host's NetworkManager profile
+  # (modules/networking/wifi.nix). The password is not here -- it's
+  # sops-encrypted in secrets/gui.yaml (wifi-password) instead, since this
+  # file isn't a secret store.
   wifiSsid = "nbn-fttp-net-5G";
 
+  # Bare-metal gui host's two disks for a ZFS RAID0 (striped) root pool
+  # (modules/disko/baremetal.nix). Only used transiently at disko-format
+  # time (partitioning); the resulting fileSystems/zpool import reference
+  # by-partlabel/by-id paths afterward regardless, same as
+  # modules/disko/proxmox.nix's own plain "/dev/sda".
+  guiRootDisk1 = "/dev/sda";
+  guiRootDisk2 = "/dev/sdb";
+
   # System
   timeZone = "Australia/Brisbane";