test(cli): probe CLI execution in vitest globalSetup

Run --version after build so smoke tests fail fast with a clear error when
runtime dependencies are missing, not only when dist/cli.js is absent.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: Array Fleet

test/global-setup.ts

@@ -1,4 +1,4 @@
-import { execSync } from "node:child_process";
+import { execSync, spawnSync } from "node:child_process";
 import { existsSync } from "node:fs";
 import { dirname, join } from "node:path";
 import { fileURLToPath } from "node:url";
@@ -11,4 +11,16 @@ export default function setup(): void {
   if (!existsSync(cli)) {
     throw new Error(`CLI build failed: ${cli} not found before running tests`);
   }
+
+  const probe = spawnSync(process.execPath, [cli, "--version"], {
+    cwd: repoRoot,
+    encoding: "utf8",
+    env: { ...process.env, MEX_TELEMETRY: "0", NO_COLOR: "1" },
+  });
+  if (probe.status !== 0) {
+    const detail = [probe.stdout, probe.stderr].filter(Boolean).join("\n");
+    throw new Error(
+      `CLI probe failed (run npm install if dependencies are missing): ${detail}`,
+    );
+  }
 }