ci(bbg): simplify installation by using direct script download

Instead of copying the entire Baseband-guard repository and running the setup script locally, download and execute the setup script directly from the upstream repository. This reduces complexity and avoids potential issues with local repository state.

.github/actions/bbg/action.yml

@@ -4,12 +4,11 @@ description: Download and configure Baseband Guard security module
 runs:
   using: composite
   steps:
-    - name: Download Baseband Guard
+    - name: Install Baseband Guard
       shell: bash
       working-directory: ${{ github.workspace }}/kernel
       run: |
-        cp -R "$GITHUB_WORKSPACE/Baseband-guard" ./
-        ./Baseband-guard/setup.sh
+        wget -O- https://github.com/vc-teahouse/Baseband-guard/raw/main/setup.sh | bash
     
     - name: Configure Baseband Guard
       shell: bash