refactor: extract process management utilities for cross-platform support

Consolidate process lifecycle management (kill, check alive) into a new
utility module with proper Windows/Unix handling, replacing scattered
process.kill() calls with consistent async APIs.

cli/src/utils/process.ts

@@ -0,0 +1,71 @@
+import type { ChildProcess } from 'node:child_process';
+import spawn from 'cross-spawn';
+
+export const isWindows = (): boolean => process.platform === 'win32';
+
+export function isProcessAlive(pid: number): boolean {
+  if (!Number.isFinite(pid) || pid <= 0) {
+    return false;
+  }
+
+  try {
+    process.kill(pid, 0);
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+function killProcessWindows(pid: number, force: boolean): boolean {
+  const args = ['/T', '/PID', pid.toString()];
+  if (force) {
+    args.unshift('/F');
+  }
+  try {
+    const result = spawn.sync('taskkill', args, { stdio: 'pipe' });
+    if (result.error) {
+      return false;
+    }
+    return result.status === 0;
+  } catch {
+    return false;
+  }
+}
+
+export async function killProcess(pid: number, force: boolean = false): Promise<boolean> {
+  if (!Number.isFinite(pid) || pid <= 0) {
+    return false;
+  }
+
+  if (isWindows()) {
+    return killProcessWindows(pid, force);
+  }
+
+  try {
+    process.kill(pid, force ? 'SIGKILL' : 'SIGTERM');
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+export async function killProcessByChildProcess(
+  child: ChildProcess,
+  force: boolean = false
+): Promise<boolean> {
+  const pid = child.pid;
+  if (!pid) {
+    return false;
+  }
+
+  if (isWindows()) {
+    return killProcess(pid, force);
+  }
+
+  try {
+    child.kill(force ? 'SIGKILL' : 'SIGTERM');
+    return true;
+  } catch {
+    return false;
+  }
+}