fix: STDIO transport stdout flush and MCP notification handling

- Wait for stdout.write callback before process.exit in STDIO transport
  to prevent truncation of large responses (e.g. grafana tools/list)
- Handle MCP notification methods (notifications/initialized, etc.) in
  router instead of returning "Method not found" error
- Use -p shorthand in config claude output

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

src/mcplocal/src/router.ts

@@ -367,6 +367,17 @@ export class McpRouter {
       case 'prompts/get':
         return this.routeNamespacedCall(request, 'name', this.promptToServer);
 
+      // Handle MCP notifications (no response expected, but return empty result if called as request)
+      case 'notifications/initialized':
+      case 'notifications/cancelled':
+      case 'notifications/progress':
+      case 'notifications/roots/list_changed':
+        return {
+          jsonrpc: '2.0',
+          id: request.id,
+          result: {},
+        };
+
       default:
         return {
           jsonrpc: '2.0',