chore: import upstream snapshot with attribution

examples/environments/.env.example

@@ -0,0 +1,20 @@
+# --- Vercel Sandbox ---
+# Snapshot ID with agent-browser + Chromium pre-installed (optional, speeds up startup)
+# Create one with: npx tsx scripts/create-snapshot.ts
+# AGENT_BROWSER_SNAPSHOT_ID=snap_xxxxxxxxxxxx
+
+# --- Sandbox Authentication ---
+# On Vercel deployments, OIDC auth is automatic. For local development,
+# provide explicit credentials:
+# VERCEL_TOKEN=
+# VERCEL_TEAM_ID=
+# VERCEL_PROJECT_ID=
+
+# --- Rate Limiting (Upstash / Vercel KV) ---
+# Automatically populated when you add Vercel KV to your project
+KV_REST_API_URL=
+KV_REST_API_TOKEN=
+
+# Optional: override default limits
+# RATE_LIMIT_PER_MINUTE=10
+# RATE_LIMIT_PER_DAY=100