chore: use Vercel deploy hook instead of auto deployment

Disable automatic git-triggered deployments via vercel.json and add a
GitHub Actions workflow to trigger deployment via hook on main push and
manual dispatch.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: tianzhou

.github/workflows/deploy.yml

@@ -0,0 +1,14 @@
+name: Deploy to Vercel
+
+on:
+  push:
+    branches:
+      - main
+  workflow_dispatch:
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Trigger Vercel Deploy Hook
+        run: curl -s -X POST "https://api.vercel.com/v1/integrations/deploy/prj_S70AajXvkWSEz2yU1NvcvfZpmm1g/y3wAh0IwTP"

vercel.json

@@ -0,0 +1,5 @@
+{
+  "git": {
+    "deploymentEnabled": false
+  }
+}