test: guard Windows setup build workflow

Add a regression test that keeps the Windows setup E2E workflow wired to the real bun run build path and the files that can regress the #1530 Bun shell crash.

This is test-only so it can be pushed without workflow scope while still preventing accidental removal of the Windows build gate.

test/windows-setup-e2e-workflow.test.ts

@@ -0,0 +1,47 @@
+/**
+ * Windows Setup E2E workflow regression guard for #1530.
+ *
+ * The unit shell-compat test proves package.json no longer contains Bun-hostile
+ * subshell redirections. This workflow-level guard makes sure the Windows E2E
+ * job keeps exercising the actual install/build path that caught the original
+ * Windows Bun crash.
+ */
+import { describe, test, expect } from 'bun:test';
+import * as fs from 'node:fs';
+import * as path from 'node:path';
+
+const WORKFLOW = path.resolve(import.meta.dir, '..', '.github', 'workflows', 'windows-setup-e2e.yml');
+const content = fs.readFileSync(WORKFLOW, 'utf-8');
+
+describe('windows-setup-e2e.yml #1530 regression coverage', () => {
+  test('runs the real Windows build path that used to crash Bun', () => {
+    expect(content).toMatch(/runs-on:\s*windows-latest/);
+    expect(content).toContain('run: bun run build');
+    expect(content).toContain('shell: bash');
+    expect(content).toContain("GSTACK_SKIP_PLAYWRIGHT: '1'");
+  });
+
+  test('is triggered by the files that can regress the Windows build chain', () => {
+    for (const triggerPath of [
+      'package.json',
+      'scripts/build.sh',
+      'scripts/write-version-files.sh',
+      'setup',
+      '.github/workflows/windows-setup-e2e.yml',
+    ]) {
+      expect(content).toContain(`- '${triggerPath}'`);
+    }
+  });
+
+  test('verifies the build outputs that prove bun run build completed', () => {
+    expect(content).toContain('Verify binaries exist');
+    for (const binary of [
+      'browse/dist/browse',
+      'browse/dist/find-browse',
+      'design/dist/design',
+      'bin/gstack-global-discover',
+    ]) {
+      expect(content).toContain(binary);
+    }
+  });
+});