feat: drop Docker Model Runner in favor of llmman (#2847)

Remove docker-model-plugin from the DX Docker package set.

llmman (https://github.com/llmmanorg/llmman) covers the same local
model runner use case and is available via Homebrew from the shared
ai-tools Brewfile (`ujust bbrew` -> ai), so the Docker plugin is no
longer needed in the image.

build_scripts/dx/00-dx.sh

@@ -82,8 +82,7 @@ dnf -y install --enablerepo=docker-ce-stable \
     docker-buildx-plugin \
     docker-ce \
     docker-ce-cli \
-    docker-compose-plugin \
-    docker-model-plugin
+    docker-compose-plugin
 
 # VSCode package from Microsoft repo
 echo "Installing VSCode from official repo..."