fix(setup): -h/--help prints usage instead of running the installer

Asking setup for help RAN the full installer — Playwright download and all.
Standard help flags now short-circuit to usage.

Contributed by @saen-ai (PR #1219).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test/setup-help.test.ts

@@ -0,0 +1,64 @@
+import { describe, test, expect } from 'bun:test';
+import { spawnSync } from 'child_process';
+import * as path from 'path';
+import * as fs from 'fs';
+
+const ROOT = path.resolve(import.meta.dir, '..');
+const SETUP_SCRIPT = path.join(ROOT, 'setup');
+
+describe('setup: --help flag (#1133)', () => {
+  test('setup script defines a usage() function', () => {
+    const content = fs.readFileSync(SETUP_SCRIPT, 'utf-8');
+    expect(content).toMatch(/^usage\(\)\s*\{/m);
+  });
+
+  test('setup script short-circuits on -h/--help before env checks', () => {
+    const content = fs.readFileSync(SETUP_SCRIPT, 'utf-8');
+    const helpIdx = content.search(/-h\|--help\)\s*usage;\s*exit 0/);
+    const bunCheckIdx = content.indexOf('command -v bun');
+    expect(helpIdx).toBeGreaterThan(-1);
+    expect(bunCheckIdx).toBeGreaterThan(-1);
+    // --help must be handled before the bun availability check so the flag
+    // works on machines that haven't installed bun yet.
+    expect(helpIdx).toBeLessThan(bunCheckIdx);
+  });
+
+  test('usage text documents every supported flag', () => {
+    const content = fs.readFileSync(SETUP_SCRIPT, 'utf-8');
+    const usageMatch = content.match(/usage\(\)\s*\{[\s\S]*?\n\}/);
+    expect(usageMatch).toBeTruthy();
+    const usage = usageMatch![0];
+    for (const flag of [
+      '--host',
+      '--prefix',
+      '--no-prefix',
+      '--team',
+      '--no-team',
+      '--quiet',
+      '--help',
+    ]) {
+      expect(usage).toContain(flag);
+    }
+  });
+
+  test('./setup --help exits 0, prints usage, and does not run installer', () => {
+    const res = spawnSync('bash', [SETUP_SCRIPT, '--help'], {
+      encoding: 'utf-8',
+      timeout: 5000,
+    });
+    expect(res.status).toBe(0);
+    expect(res.stdout).toContain('Usage:');
+    expect(res.stdout).toContain('gstack setup');
+    // Hard guarantee it short-circuited — none of the install-side output appears.
+    expect(res.stdout).not.toMatch(/Installing|bun install|Building|gen:skill-docs/);
+  });
+
+  test('./setup -h is equivalent to ./setup --help', () => {
+    const res = spawnSync('bash', [SETUP_SCRIPT, '-h'], {
+      encoding: 'utf-8',
+      timeout: 5000,
+    });
+    expect(res.status).toBe(0);
+    expect(res.stdout).toContain('Usage:');
+  });
+});