Try exiting the JVM gracefully when stdin is closed

Author: nquinquenel

src/main/java/org/sonarsource/sonarqube/mcp/transport/StdioServerTransportProvider.java

@@ -252,6 +252,8 @@ private void startInboundProcessing() {
               session.close();
             }
             inboundSink.tryEmitComplete();
+            // Exit the JVM when stdin closes so Docker --rm can clean up the container
+            System.exit(0);
           }
         });
       }