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/main/nodecg/platform-process-killer.ts

@@ -0,0 +1,54 @@
+import { ChildProcess, SpawnOptions } from "node:child_process";
+
+export type PlatformProcessKillerDeps = {
+  platform: NodeJS.Platform;
+  spawnProcess: (command: string, args: string[], options: SpawnOptions) => ChildProcess;
+  killProcess: (pid: number, signal: NodeJS.Signals) => void;
+  log: (...args: unknown[]) => void;
+};
+
+export function killProcessTree(pid: number, signal: NodeJS.Signals, deps: PlatformProcessKillerDeps): boolean {
+  if (!Number.isSafeInteger(pid) || pid <= 0) {
+    deps.log(`Invalid pid for process tree termination: ${pid}`);
+    return false;
+  }
+
+  if (deps.platform === "win32") {
+    return killWindowsProcessTree(pid, signal, deps);
+  }
+
+  return killPosixProcessTree(pid, signal, deps.killProcess);
+}
+
+function killWindowsProcessTree(
+  pid: number,
+  signal: NodeJS.Signals,
+  deps: Pick<PlatformProcessKillerDeps, "spawnProcess" | "log">,
+): boolean {
+  const args = ["/pid", String(pid), "/T", ...(signal === "SIGKILL" ? ["/F"] : [])];
+  const killer = deps.spawnProcess("taskkill", args, {
+    stdio: "ignore",
+    shell: false,
+    windowsHide: true,
+  });
+
+  killer.on("error", (error) => {
+    deps.log(`taskkill error for pid=${pid}`, error);
+  });
+
+  return true;
+}
+
+function killPosixProcessTree(pid: number, signal: NodeJS.Signals, killProcess: PlatformProcessKillerDeps["killProcess"]): boolean {
+  try {
+    killProcess(-pid, signal);
+    return true;
+  } catch {
+    try {
+      killProcess(pid, signal);
+      return true;
+    } catch {
+      return false;
+    }
+  }
+}