Add users to seat group when seatd is selected (#4578)

* Add users to seat group when seatd is selected

When a desktop profile uses seatd for seat access, the user must be
in the seat group for the compositor to access input devices. Without
this, sway/hyprland/niri/labwc fail to start after installation.

* Move seat access provisioning into DesktopProfile.provision()

The four Wayland profiles (Hyprland, Sway, niri, labwc) each duplicated a
provision() override calling provision_seat_access(). Move that into the
base DesktopProfile.provision() loop, which already iterates the selected
profiles, and read CustomSetting.SeatAccess from each. The None check now
lives at the call site (walrus), so provision_seat_access() takes a plain
str. This removes the per-profile overrides and their TYPE_CHECKING imports.

* Use top-level imports in seat access utils

The Installer and User imports were under a TYPE_CHECKING guard, but
they cause no circular import (bspwm.py already imports both at top
level). Move them to module scope per review feedback.

archinstall/default_profiles/desktop.py

@@ -1,6 +1,7 @@
 from typing import TYPE_CHECKING, Self, override
 
-from archinstall.default_profiles.profile import DisplayServerType, GreeterType, Profile, ProfileType, SelectResult
+from archinstall.default_profiles.desktops.utils import provision_seat_access
+from archinstall.default_profiles.profile import CustomSetting, DisplayServerType, GreeterType, Profile, ProfileType, SelectResult
 from archinstall.lib.log import info
 from archinstall.lib.menu.helpers import Selection
 from archinstall.lib.profile.profiles_handler import profile_handler
@@ -94,6 +95,9 @@ class DesktopProfile(Profile):
 		for profile in self.current_selection:
 			profile.provision(install_session, users)
 
+			if seat_access := profile.custom_settings.get(CustomSetting.SeatAccess):
+				provision_seat_access(install_session, users, seat_access)
+
 	@override
 	def install(self, install_session: Installer) -> None:
 		# Install common packages for all desktop environments

archinstall/default_profiles/desktops/utils.py

@@ -1,6 +1,8 @@
 from enum import Enum
 
+from archinstall.lib.installer import Installer
 from archinstall.lib.menu.helpers import Selection
+from archinstall.lib.models.users import User
 from archinstall.lib.translationhandler import tr
 from archinstall.tui.menu_item import MenuItem, MenuItemGroup
 from archinstall.tui.result import ResultType
@@ -11,6 +13,16 @@ class SeatAccess(Enum):
 	polkit = 'polkit'
 
 
+def provision_seat_access(
+	install_session: Installer,
+	users: list[User],
+	seat_access: str,
+) -> None:
+	if seat_access == SeatAccess.seatd.value:
+		for user in users:
+			install_session.arch_chroot(f'usermod -a -G seat {user.username}')
+
+
 async def select_seat_access(profile_name: str, default: str | None) -> SeatAccess:
 	header = tr('{} needs access to your seat').format(profile_name)
 	header += f' ({tr("collection of hardware devices i.e. keyboard, mouse")})' + '\n'