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

iso-profiles/antergos/live-overlay/etc/calamares/modules/packagechooser_dm.conf

@@ -29,7 +29,7 @@ items:
               hidden: true
               packages:
                 - sddm
-                - sddm-openrc
+                - sddm-dinit
                 - antergos-sddm-theme
 
     - id: LightDM
@@ -51,7 +51,7 @@ items:
               hidden: true
               packages:
                 - lightdm
-                - lightdm-openrc
+                - lightdm-dinit
 
     - id: LXDM
       name: lxdm
@@ -72,7 +72,7 @@ items:
               hidden: true
               packages:
                 - lxdm
-                - lxdm-openrc
+                - lxdm-dinit
 
     - id: LY
       name: ly
@@ -93,4 +93,4 @@ items:
               hidden: true
               packages:
                 - ly
-                - ly-openrc
+                - ly-dinit