Stage 4: Calamares installer and Btrfs snapshots (0.2.0)

- Package Calamares 3.4.3 (Qt6, widgets UI) with xbps-src.
- das-installer: Calamares setup for Void/runit with Das OS branding and
  slides. It copies the clean live image (live-base), builds locales and the
  host-only initramfs, rewrites kernels without sparse tails (GRUB 2.12 cannot
  read Btrfs holes at the end of a file), then removes itself.
- das-snapshots: flat Btrfs layout (@, @home, @snapshots, @var_log,
  @var_cache_xbps), snapper with hourly snapshots via cronie, grub-btrfs menu,
  snapper-rollback, and a dracut module that boots read-only snapshots with
  a RAM overlay.
- das-settings 0.2.0: start LightDM with the system locale.
- Live image: GRUB, efibootmgr and the new packages; Das OS /etc/issue.
- Build: wipe stale destdirs before building packages.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

srcpkgs/das-installer/files/calamares/modules/partition.conf

@@ -0,0 +1,29 @@
+---
+efi:
+    mountPoint: "/boot/efi"
+    recommendedSize: 512MiB
+    minimumSize: 64MiB
+    label: "EFI"
+
+userSwapChoices:
+    - none
+    - small
+    - suspend
+initialSwapChoice: none
+
+drawNestedPartitions: false
+alwaysShowPartitionLabels: true
+allowManualPartitioning: true
+initialPartitioningChoice: none
+
+# Btrfs subvolumes (see mount.conf) give snapper snapshots and rollback.
+defaultFileSystemType: "btrfs"
+availableFileSystemTypes: [ "btrfs", "ext4", "xfs" ]
+
+# Disk encryption needs extra initramfs and GRUB setup that Das OS does not
+# have yet.
+enableLuksAutomatedPartitioning: false
+
+essentialMounts: [ "live-*", "control", "ventoy" ]
+lvm:
+    enable: false