feat: Enhance NodeCG process management and add IPC security tests

src/tests/application-controller.test.ts

@@ -1,5 +1,4 @@
 import assert from "node:assert/strict";
-import { EventEmitter } from "node:events";
 import test from "node:test";
 
 import { createApplicationController, ApplicationWindow } from "../main/app/application-controller";
@@ -68,7 +67,6 @@ function createMockManager(events: string[]): NodecgProcessManager {
   return {
     startNodecgProcess: async () => {
       events.push("start-nodecg");
-      return new EventEmitter() as import("node:child_process").ChildProcess;
     },
     waitForNodecgReady: async () => {
       events.push("wait-nodecg");
@@ -76,7 +74,7 @@ function createMockManager(events: string[]): NodecgProcessManager {
     stopNodecgProcessGracefully: async () => {
       events.push("stop-nodecg");
     },
-    getProcess: () => null,
+    getState: () => "running",
   };
 }