fix(installer): declare extra LUKS devices for multi-disk boot

A multi-disk install builds one LUKS container per drive joined into a
single multi-device BTRFS (-d single -m raid1). nixos-generate-config
only emits boot.initrd.luks.devices for the main drive — every subvolume
mounts through /dev/mapper/crypted_main, so the other members are
invisible to it. The installed system then unlocked only the main drive,
the array never assembled, and boot hung. Invisible single-disk, fatal
multi-disk (matches a real-hardware report).

generate_flake_config now writes, into hardware-selection.nix, a
boot.initrd.luks.devices entry for each extra drive (UUID resolved via
disko's partlabel; mapper name mirrors disko-config.nix's sanitize) and
re-asserts the x-systemd.requires= mount options disko sets but which
nixos-generate-config strips.

Verified end-to-end in a 3-disk UEFI QEMU VM: reproduced the bug, applied
the fix, ran a real nixos-install onto the array, and rebooted from the
disks — one passphrase unlocked all three containers, the 3-device BTRFS
assembled, and the system reached login.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

installer/install.sh

@@ -1467,6 +1467,42 @@ generate_flake_config() {
         impermanence_opt=$'nomarchy.system.impermanence.enable = true;\n  nomarchy.system.impermanence.mainLuksName = "'"$_main_luks_name"$'";\n  nomarchy.system.impermanence.user = "'"$USERNAME"$'";'
     fi
 
+    # Multi-disk LUKS unlock. `nixos-generate-config` only emits a
+    # boot.initrd.luks.devices entry for the container that backs a
+    # fileSystems device — and every subvolume mount points at the main
+    # /dev/mapper/crypted_main. The extra drives in a multi-disk BTRFS array
+    # are members of that filesystem but are invisible through the
+    # device-mapper path it traces, so it never declares them. Without the
+    # entries below, initrd unlocks only the main drive, the multi-device
+    # BTRFS can never be assembled, and the installed system hangs at boot
+    # (the failure is invisible single-disk and only bites multi-disk
+    # hardware). We also re-assert the x-systemd.requires mount options disko
+    # set on every BTRFS mount (installer/disko-config.nix) but which
+    # nixos-generate-config drops — they make systemd-initrd wait for ALL
+    # members before mounting. Drive→mapper/partlabel naming mirrors
+    # disko-config.nix's `sanitize` (replace '/' and '-' with '_').
+    local EXTRA_LUKS_OPTS=""
+    local _ld=($TARGET_DRIVE)
+    if (( ${#_ld[@]} > 1 )); then
+        local _luks_lines="" _requires="" _i _extra _san _mapper _partlabel _uuid
+        for (( _i=1; _i<${#_ld[@]}; _i++ )); do
+            _extra="${_ld[$_i]}"
+            _san="${_extra//\//_}"; _san="${_san//-/_}"   # /dev/sdb -> _dev_sdb
+            _mapper="crypted_${_san}"
+            _partlabel="disk-extra_${_san}-luks"
+            _uuid=$(blkid -s UUID -o value "/dev/disk/by-partlabel/$_partlabel")
+            _luks_lines+=$'\n'"  boot.initrd.luks.devices.\"$_mapper\".device = \"/dev/disk/by-uuid/$_uuid\";"
+            _luks_lines+=$'\n'"  boot.initrd.luks.devices.\"$_mapper\".allowDiscards = true;"
+            _requires+=" \"x-systemd.requires=/dev/mapper/$_mapper\""
+        done
+        # BTRFS subvolume mountpoints — must match installer/disko-config.nix.
+        local _mp _fs_lines=""
+        for _mp in / /persist /home /nix /var/log /.snapshots; do
+            _fs_lines+=$'\n'"  fileSystems.\"$_mp\".options = [$_requires ];"
+        done
+        EXTRA_LUKS_OPTS="$_luks_lines"$'\n'"$_fs_lines"
+    fi
+
     local PROFILE_SYSTEM_OPTS=""
     local PROFILE_HOME_PACKAGES=""
 
@@ -1589,7 +1625,7 @@ FLAKE_EOF
   imports = [
     $HARDWARE_MODULES
   ];
-  $NOMARCHY_HW_OPTS
+  $NOMARCHY_HW_OPTS$EXTRA_LUKS_OPTS
 }
 EOF