fix: enhance gateway logging for Windows dev restart debugging (#665)

Add comprehensive debug logging throughout the gateway lifecycle to
help troubleshoot nodemon restart issues on Windows, where SIGTERM
is used instead of SIGUSR2.

Changes:
- Enhanced shutdown handler to log all signals and env var states
- Gateway manager now logs process detachment mode explicitly
- Added environment variable confirmation on bootstrap
- Updated gateway-development.md with new debug logs and troubleshooting steps

Benefits:
- Easier troubleshooting of gateway lifecycle issues
- Clear visibility into signal handling during nodemon restarts
- Better cross-platform development experience
- Production behavior remains unchanged

Testing:
- ✅ Windows: Gateways persist across nodemon restarts
- ✅ macOS/Linux: Existing SIGUSR2 behavior preserved
- ✅ Production: Default shutdown cleanup unchanged
- ✅ Backward compatibility: No breaking changes

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/server/src/index.ts

@@ -85,6 +85,10 @@ export async function bootstrap() {
 
   const authToken = await getToken()
   await initLoginLimiter()
+
+  // Debug: log environment variable
+  console.log('[bootstrap] HERMES_WEB_UI_STOP_GATEWAYS_ON_SHUTDOWN =', process.env.HERMES_WEB_UI_STOP_GATEWAYS_ON_SHUTDOWN)
+
   const app = new Koa()
 
   await initGatewayManager()