refactor: move setup scripts out of src/ to reduce build token count

Setup scripts are standalone CLI tools run via tsx with no runtime
imports from the main app. Moving them out of src/ excludes them from
the tsc build output and reduces the compiled bundle size.

- git mv src/setup/ setup/
- Fix imports to use ../src/logger.js and ../src/config.js
- Update package.json, vitest.config.ts, SKILL.md references
- Fix platform tests to be cross-platform (macOS + Linux)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

setup/index.ts

@@ -0,0 +1,52 @@
+/**
+ * Setup CLI entry point.
+ * Usage: npx tsx setup/index.ts --step <name> [args...]
+ */
+import { logger } from '../src/logger.js';
+import { emitStatus } from './status.js';
+
+const STEPS: Record<string, () => Promise<{ run: (args: string[]) => Promise<void> }>> = {
+  environment: () => import('./environment.js'),
+  container: () => import('./container.js'),
+  'whatsapp-auth': () => import('./whatsapp-auth.js'),
+  groups: () => import('./groups.js'),
+  register: () => import('./register.js'),
+  mounts: () => import('./mounts.js'),
+  service: () => import('./service.js'),
+  verify: () => import('./verify.js'),
+};
+
+async function main(): Promise<void> {
+  const args = process.argv.slice(2);
+  const stepIdx = args.indexOf('--step');
+
+  if (stepIdx === -1 || !args[stepIdx + 1]) {
+    console.error(`Usage: npx tsx setup/index.ts --step <${Object.keys(STEPS).join('|')}> [args...]`);
+    process.exit(1);
+  }
+
+  const stepName = args[stepIdx + 1];
+  const stepArgs = args.filter((a, i) => i !== stepIdx && i !== stepIdx + 1 && a !== '--');
+
+  const loader = STEPS[stepName];
+  if (!loader) {
+    console.error(`Unknown step: ${stepName}`);
+    console.error(`Available steps: ${Object.keys(STEPS).join(', ')}`);
+    process.exit(1);
+  }
+
+  try {
+    const mod = await loader();
+    await mod.run(stepArgs);
+  } catch (err) {
+    const message = err instanceof Error ? err.message : String(err);
+    logger.error({ err, step: stepName }, 'Setup step failed');
+    emitStatus(stepName.toUpperCase(), {
+      STATUS: 'failed',
+      ERROR: message,
+    });
+    process.exit(1);
+  }
+}
+
+main();