feat: Implement application bootstrap and window management

- Added bootstrap functionality to initialize the Electron application.
- Created a new paths module to manage application paths and URLs.
- Introduced a shutdown service to handle graceful application shutdowns.
- Refactored error logging to use a dedicated logger module.
- Implemented process killing logic for NodeCG processes across platforms.
- Established navigation policies for internal and external URL handling in windows.
- Developed window service for creating and managing application windows.
- Added tests for application paths, application controller, navigation policies, process killer, and shutdown service.

src/tests/platform-process-killer.test.ts

@@ -0,0 +1,65 @@
+import assert from "node:assert/strict";
+import { EventEmitter } from "node:events";
+import { SpawnOptions } from "node:child_process";
+import test from "node:test";
+
+import { killProcessTree } from "../main/nodecg/platform-process-killer";
+
+test("killProcessTree validates pid before building Windows taskkill command", () => {
+  const spawnCalls: Array<{ command: string; args: string[]; options: SpawnOptions }> = [];
+
+  const killed = killProcessTree(Number.NaN, "SIGTERM", {
+    platform: "win32",
+    spawnProcess: (command, args, options) => {
+      spawnCalls.push({ command, args, options });
+      return new EventEmitter() as import("node:child_process").ChildProcess;
+    },
+    killProcess: () => undefined,
+    log: () => undefined,
+  });
+
+  assert.equal(killed, false);
+  assert.deepEqual(spawnCalls, []);
+});
+
+test("killProcessTree builds a narrow Windows taskkill invocation", () => {
+  const spawnCalls: Array<{ command: string; args: string[]; options: SpawnOptions }> = [];
+
+  const killed = killProcessTree(1234, "SIGKILL", {
+    platform: "win32",
+    spawnProcess: (command, args, options) => {
+      spawnCalls.push({ command, args, options });
+      return new EventEmitter() as import("node:child_process").ChildProcess;
+    },
+    killProcess: () => undefined,
+    log: () => undefined,
+  });
+
+  assert.equal(killed, true);
+  assert.equal(spawnCalls[0]?.command, "taskkill");
+  assert.deepEqual(spawnCalls[0]?.args, ["/pid", "1234", "/T", "/F"]);
+  assert.equal(spawnCalls[0]?.options.shell, false);
+  assert.equal(spawnCalls[0]?.options.windowsHide, true);
+});
+
+test("killProcessTree falls back from POSIX process group to child pid", () => {
+  const killCalls: Array<{ pid: number; signal: NodeJS.Signals }> = [];
+
+  const killed = killProcessTree(1234, "SIGTERM", {
+    platform: "linux",
+    spawnProcess: () => new EventEmitter() as import("node:child_process").ChildProcess,
+    killProcess: (pid, signal) => {
+      killCalls.push({ pid, signal });
+      if (pid < 0) {
+        throw new Error("process group unavailable");
+      }
+    },
+    log: () => undefined,
+  });
+
+  assert.equal(killed, true);
+  assert.deepEqual(killCalls, [
+    { pid: -1234, signal: "SIGTERM" },
+    { pid: 1234, signal: "SIGTERM" },
+  ]);
+});