Add Vercel deploy workflow for install scripts

Serves openclaw/install.sh at install.cmem.ai/openclaw.sh via Vercel.
Auto-deploys on changes to openclaw/install.sh on main.

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

install/vercel.json

@@ -0,0 +1,12 @@
+{
+  "$schema": "https://openapi.vercel.sh/vercel.json",
+  "headers": [
+    {
+      "source": "/(.*)\\.sh",
+      "headers": [
+        { "key": "Content-Type", "value": "text/plain; charset=utf-8" },
+        { "key": "Cache-Control", "value": "public, max-age=300, s-maxage=60" }
+      ]
+    }
+  ]
+}