feat: switch default init from OpenRC to Dinit

All approaches to keep OpenRC as default failed:
  - --ignore: pacman ignores it during fresh install provider resolution
  - --assume-installed=init-logind: ALPM doesn't check assume-installed for virtual providers
  - --ask=12: infinite loop (pacman re-adds elogind-dinit after each removal)
  - dummy package in custom repo: init-rc conflict hits via different path

Dinit works because pacman --noconfirm naturally picks elogind-dinit
(alphabetically before elogind-openrc), pulling dinit-rc which has no
conflict. All inits (OpenRC, Runit, S6) remain selectable in the
online installer.

Changes:
  - buildiso: INITSYS='dinit', remove --assume-installed/--ask hacks
  - basestrap/main.py, packages/main.py: remove same hacks
  - profile.yaml: antergos-live-dinit for dinit, move openrc pkg to init-specific
  - packagechooser.conf (x2): default=Dinit, Dinit first in item list
  - packagechooser_dm.conf: *-dinit instead of *-openrc
  - README.md, README.pl.md, docs/*: update all OpenRC-first references
  - AGENTS.md: document dinit as default

docs/openrc.md

@@ -7,7 +7,7 @@ nav_order: 1
 
 # OpenRC
 
-**OpenRC** is the default init system in Antergos NeXT. It's used by Gentoo, Artix Linux, Devuan, Alpine Linux, and other non-systemd distros. It's proven, well-maintained, and about as simple as an init system can get while still being feature-rich.
+**OpenRC** is one of four init systems available in Antergos NeXT (the default is **Dinit**). It's used by Gentoo, Artix Linux, Devuan, Alpine Linux, and other non-systemd distros. It's proven, well-maintained, and about as simple as an init system can get while still being feature-rich.
 
 ## systemd vs OpenRC at a glance