Fix VHS demo workflow to only run on merges to default branch (#59)

Co-authored-by: alvarosanchez <153880+alvarosanchez@users.noreply.github.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

Author: Copilot

.github/workflows/vhs.yml

@@ -2,7 +2,10 @@ name: VHS Demo
 
 on:
   workflow_dispatch:
-  pull_request:
+  push:
+    branches:
+      - master
+      - main
     paths:
       - '.github/workflows/vhs.yml'
       - 'docs/demo/**'
@@ -14,7 +17,7 @@ permissions:
   contents: write
 
 concurrency:
-  group: vhs-demo-${{ github.event.pull_request.number || github.ref }}
+  group: vhs-demo-${{ github.ref }}
   cancel-in-progress: true
 
 jobs:
@@ -58,7 +61,7 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         with:
           commit_message: 'docs: update generated VHS demo'
-          branch: ${{ github.head_ref || github.ref_name }}
+          branch: ${{ github.ref_name }}
           commit_user_name: vhs-action 📼
           commit_user_email: actions@github.com
           commit_author: vhs-action 📼 <actions@github.com>