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/branding/dasos/branding.desc

@@ -0,0 +1,37 @@
+---
+componentName: dasos
+
+welcomeStyleCalamares: false
+welcomeExpandingLogo: true
+windowExpanding: normal
+windowSize: 960px,640px
+windowPlacement: center
+sidebar: widget
+navigation: widget
+
+strings:
+    productName: "Das OS"
+    shortProductName: "Das OS"
+    version: "0.2.0"
+    shortVersion: "0.2"
+    versionedName: "Das OS 0.2.0"
+    shortVersionedName: "Das OS 0.2"
+    bootloaderEntryName: "Das OS"
+    productUrl: "https://git.das.org.ua/das/Das-OS"
+    supportUrl: "https://git.das.org.ua/das/Das-OS/issues"
+
+images:
+    productIcon: "/usr/share/icons/hicolor/scalable/apps/das-logo.svg"
+    productLogo: "/usr/share/icons/hicolor/scalable/apps/das-logo.svg"
+    productWelcome: "welcome.svg"
+
+slideshow:
+    - "slide-1.svg"
+    - "slide-2.svg"
+    - "slide-3.svg"
+
+style:
+    SidebarBackground: "#1b1f27"
+    SidebarText: "#e3e6ec"
+    SidebarTextCurrent: "#1b1f27"
+    SidebarBackgroundCurrent: "#ffd23f"