fix: harden windows cli launch

src/agents/shell-utils.ts

@@ -1,5 +1,22 @@
+import fs from "node:fs";
+import path from "node:path";
 import { spawn } from "node:child_process";
 
+function resolvePowerShellPath(): string {
+  const systemRoot = process.env.SystemRoot || process.env.WINDIR;
+  if (systemRoot) {
+    const candidate = path.join(
+      systemRoot,
+      "System32",
+      "WindowsPowerShell",
+      "v1.0",
+      "powershell.exe",
+    );
+    if (fs.existsSync(candidate)) return candidate;
+  }
+  return "powershell.exe";
+}
+
 export function getShellConfig(): { shell: string; args: string[] } {
   if (process.platform === "win32") {
     // Use PowerShell instead of cmd.exe on Windows.
@@ -8,7 +25,7 @@ export function getShellConfig(): { shell: string; args: string[] } {
     // When Node.js spawns cmd.exe with piped stdio, these utilities produce no output.
     // PowerShell properly captures and redirects their output to stdout.
     return {
-      shell: "powershell.exe",
+      shell: resolvePowerShellPath(),
       args: ["-NoProfile", "-NonInteractive", "-Command"],
     };
   }