feat: add GitHub Pages docs site (Just the Docs), split packagechooser, disable IA upload

- docs/: new 13-page Jekyll site with Just the Docs theme
  - Home, Building, Installer, Packages, CI/CD, Development
  - Desktop Environments (with GNOME joke), Wallpapers, Launcher
  - Overlays, Root Overlay, Live Overlay
- .github/workflows/pages.yml: build & deploy docs from docs/ on
  push to master (only when docs/ changes)
- .github/workflows/build.yml: temporarily disable Internet Archive
  upload (if: false) until ISO is stable
- live-overlay/settings.conf: add instances section for init + desktop
  packagechooser instances
- live-overlay/modules/packagechooser_init.conf: init system selector
  (OpenRC, Runit, S6, Dinit) via netinstall-add method
- live-overlay/modules/packagechooser_desktop.conf: DE selector
  (Plasma, Xfce, Cinnamon, MATE, LXQt, i3, Sway, Hyprland + No Desktop)
  via legacy method
- README.md, AGENTS.md: fix sudo buildiso -> sudo ./buildiso, add note
  about system buildiso lacking --overwrite='*'
- .gitignore: add docs/_site/

docs/installer.md

@@ -0,0 +1,60 @@
+---
+title: Installer
+layout: default
+nav_order: 3
+---
+
+# Calamares Installer
+
+Uses [Calamares](https://codeberg.org/calamares/calamares) with two modes and custom branding.
+
+## Modes
+
+| Mode | Description |
+|------|-------------|
+| **Offline** | Unpacks a KDE Plasma squashfs — no internet needed |
+| **Online** | Netinstall with init system choice + desktop selection |
+
+The launcher (`calamares-next`) presents a mode picker before launching Calamares.
+
+## Key differences from upstream
+
+- `dracut`/`dracutlukscfg` replaced with `initcpiocfg`/`initcpio`/`luksopenswaphookcfg` (Artix uses mkinitcpio, not dracut)
+- `services-openrc` module instead of `services-systemd`
+- `removeuser` step removed, `postcfg` added
+- `packagechooser` module compiled in (upstream skips it)
+
+## Init system selector (online)
+
+Users choose from: **OpenRC**, **Runit**, **S6**, **Dinit**.
+
+Implemented as a `packagechooser` instance with `method: netinstall-add` — the selected init pulls its associated packages.
+
+## Desktop selector (online)
+
+Users choose from: **Plasma**, **Xfce**, **Cinnamon**, **MATE**, **LXQt**, **i3**, **Sway**, **Hyprland**, or **No Desktop**.
+
+Implemented as a separate `packagechooser` instance with `method: legacy`. "No Desktop" installs only the base system (TTY-only).
+
+## Available desktops
+
+| Desktop | Artix Repo | Group/Packages |
+|---------|------------|----------------|
+| Plasma | world | `plasma` group |
+| Xfce | galaxy | `xfce4` group |
+| Cinnamon | galaxy | Individual packages |
+| MATE | galaxy | `mate` + `mate-extra` groups |
+| LXQt | galaxy | `lxqt` group |
+| i3 | world | `i3` group |
+| Sway | world | `sway` + related packages |
+| Hyprland | world | `hyprland` |
+
+> **Note:** Budgie is not available in any Artix repo and has been removed from all configs and slideshows.
+
+## Offline mode
+
+No packagechooser. Uses `unpackfs` to deploy a pre-built KDE Plasma squashfs, then `initcpiocfg` + `initcpio` for mkinitcpio configuration.
+
+## Branding
+
+Custom branding lives in the `calamares-branding-antergos-next` package, installed to `/etc/calamares/branding/default/`. The `componentName` in `branding.desc` must match its directory name.