perf(deploy): pre-install node_modules in CI and enable always-on to fix slow cold start

- CI now runs pnpm install and includes node_modules in the zip artifact
- startup.sh simplified: removed pnpm install fallback, uses direct bin path instead of npx
- Azure Web App always-on enabled to prevent cold starts

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

langgraph/startup.sh

@@ -9,17 +9,5 @@ cd /home/site/wwwroot
 touch .env
 mkdir -p .langgraph_api
 
-# Install pnpm globally if not available
-if ! command -v pnpm &> /dev/null; then
-  echo "Installing pnpm..."
-  npm install -g pnpm@10
-fi
-
-# Install dependencies if node_modules is missing (Oryx should have done this, but fallback)
-if [ ! -d "node_modules" ]; then
-  echo "node_modules not found, installing dependencies..."
-  pnpm install --frozen-lockfile
-fi
-
 echo "Starting LangGraph server on port ${PORT:-8080}..."
-exec npx langgraphjs dev --host 0.0.0.0 --port ${PORT:-8080} --no-browser
+exec ./node_modules/.bin/langgraphjs dev --host 0.0.0.0 --port ${PORT:-8080} --no-browser