fix(yafti): Revert to using grep and remove direct usage of image identifiers

Sourcing these doesn't seem to cut it as yafti doesn't acknowledge them so instead just use
cat to obtain the file contents for the same result

system_files/deck/shared/usr/share/ublue-os/firstboot/launcher/autostart.sh

@@ -1,8 +1,5 @@
 #!/usr/bin/env bash
 
-# Source Bazzite defaults
-source /etc/default/bazzite
-
 # Simply launches the "yafti" GUI with the uBlue image's configuration.
 /usr/bin/yafti /usr/share/ublue-os/firstboot/yafti.yml
 

system_files/deck/shared/usr/share/ublue-os/firstboot/yafti.yml

@@ -249,7 +249,7 @@ screens:
     values:
       title: "GNOME Theme"
       condition:
-        run: [[ ${BASE_IMAGE_NAME} == 'silverblue' ]]
+        run: grep -q 'silverblue' <<< $(cat /etc/default/bazzite)
       links:
       - "Vapor Theme":
           run: just --unstable enable-vapor-theme

system_files/desktop/shared/usr/share/ublue-os/firstboot/launcher/autostart.sh

@@ -1,7 +1,4 @@
 #!/usr/bin/env bash
 
-# Source Bazzite defaults
-source /etc/default/bazzite
-
 # Simply launches the "yafti" GUI with the uBlue image's configuration.
 /usr/bin/yafti /usr/share/ublue-os/firstboot/yafti.yml

system_files/desktop/shared/usr/share/ublue-os/firstboot/yafti.yml

@@ -93,14 +93,12 @@ screens:
     values:
       title: AMD Additions
       condition:
-        run: [[ ${IMAGE_FLAVOR} == 'main' ]]
+        run: grep -q 'main' <<< $(cat /etc/default/bazzite)
       show_terminal: true
       package_manager: yafti.plugin.run
       groups:
         CoreCtrl:
           description: AMD GPU Overclocking
-          condition:
-            run: grep -qv "nvidia" <<< $(cat /etc/default/bazzite)
           default: false
           packages:
           - Install CoreCtrl: just --unstable install-corectrl
@@ -109,7 +107,7 @@ screens:
     values:
       title: Nvidia Additions
       condition:
-        run: [[ ${IMAGE_FLAVOR} == 'nvidia' ]]
+        run: grep -q 'nvidia' <<< $(cat /etc/default/bazzite)
       show_terminal: true
       package_manager: yafti.plugin.run
       groups:
@@ -162,7 +160,7 @@ screens:
           - Bottles: com.usebottles.bottles
           - Chiaki (PlayStation Remote Play): re.chiaki.Chiaki
           - Discord: com.discordapp.Discord
-          - DOSBox Staging: io.github.dosbox-staging 
+          - DOSBox Staging: io.github.dosbox-staging
           - GeForce NOW Electron: io.github.hmlendea.geforcenow-electron
           - Heroic Games Launcher (GOG &amp; Epic): com.heroicgameslauncher.hgl
           - itch: io.itch.itch
@@ -270,7 +268,7 @@ screens:
     values:
       title: "GNOME Theme"
       condition:
-        run: [[ ${BASE_IMAGE_NAME} == 'silverblue' ]]
+        run: grep -q 'silverblue' <<< $(cat /etc/default/bazzite)
       links:
       - "Vapor Theme":
           run: just --unstable enable-vapor-theme