Remove broken reference to checkout of plumber_core code in Copilot setup workflow

Author: lasa01

.github/copilot-instructions.md

@@ -49,7 +49,6 @@
 ## Integration Points
 - **External:**
   - Steam game detection (auto/manual)
-  - Rust backend (`plumber_core` repo) checked out for reference in `/temp/plumber_core`
   - Blender API (via `bpy` module)
 - **Internal:**
   - Custom Blender properties for imported metadata (see README)

.github/workflows/copilot-setup-steps.yml

@@ -27,12 +27,6 @@ jobs:
     steps:
       - name: Checkout Plumber code
         uses: actions/checkout@v4
-    
-      - name: Checkout plumber_core code for reference
-        uses: actions/checkout@v4
-        with:
-          repository: lasa01/plumber_core
-          path: /temp/plumber_core
 
       - name: Set up Python
         uses: actions/setup-python@v5