fix: install Auggie CLI before running the action

Add step to install @augmentcode/auggie globally before running the
assistant. The Auggie SDK spawns the auggie CLI binary, which needs
to be installed on the runner.

This fixes the 'spawn auggie ENOENT' error.

Author: Tulga Tsogtgerel

assistant/action.yml

@@ -69,6 +69,10 @@ runs:
       with:
         node-version: 22
 
+    - name: Install Auggie CLI
+      run: npm install -g @augmentcode/auggie
+      shell: bash
+
     - name: Install Action Dependencies
       run: npm install --production
       shell: bash