fix(shell): prefer PowerShell 7 on Windows with tested fallbacks (#25684)

src/agents/shell-utils.ts

@@ -2,7 +2,27 @@ import { spawn } from "node:child_process";
 import fs from "node:fs";
 import path from "node:path";
 
-function resolvePowerShellPath(): string {
+export function resolvePowerShellPath(): string {
+  // Prefer PowerShell 7 when available; PS 5.1 lacks "&&" support.
+  const programFiles = process.env.ProgramFiles || process.env.PROGRAMFILES || "C:\\Program Files";
+  const pwsh7 = path.join(programFiles, "PowerShell", "7", "pwsh.exe");
+  if (fs.existsSync(pwsh7)) {
+    return pwsh7;
+  }
+
+  const programW6432 = process.env.ProgramW6432;
+  if (programW6432 && programW6432 !== programFiles) {
+    const pwsh7Alt = path.join(programW6432, "PowerShell", "7", "pwsh.exe");
+    if (fs.existsSync(pwsh7Alt)) {
+      return pwsh7Alt;
+    }
+  }
+
+  const pwshInPath = resolveShellFromPath("pwsh");
+  if (pwshInPath) {
+    return pwshInPath;
+  }
+
   const systemRoot = process.env.SystemRoot || process.env.WINDIR;
   if (systemRoot) {
     const candidate = path.join(