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/environment.ts

@@ -0,0 +1,86 @@
+/**
+ * Step: environment — Detect OS, Node, container runtimes, existing config.
+ * Replaces 01-check-environment.sh
+ */
+import fs from 'fs';
+import path from 'path';
+
+import Database from 'better-sqlite3';
+
+import { STORE_DIR } from '../src/config.js';
+import { logger } from '../src/logger.js';
+import { commandExists, getPlatform, isHeadless, isWSL } from './platform.js';
+import { emitStatus } from './status.js';
+
+export async function run(_args: string[]): Promise<void> {
+  const projectRoot = process.cwd();
+
+  logger.info('Starting environment check');
+
+  const platform = getPlatform();
+  const wsl = isWSL();
+  const headless = isHeadless();
+
+  // Check Apple Container
+  let appleContainer: 'installed' | 'not_found' = 'not_found';
+  if (commandExists('container')) {
+    appleContainer = 'installed';
+  }
+
+  // Check Docker
+  let docker: 'running' | 'installed_not_running' | 'not_found' = 'not_found';
+  if (commandExists('docker')) {
+    try {
+      const { execSync } = await import('child_process');
+      execSync('docker info', { stdio: 'ignore' });
+      docker = 'running';
+    } catch {
+      docker = 'installed_not_running';
+    }
+  }
+
+  // Check existing config
+  const hasEnv = fs.existsSync(path.join(projectRoot, '.env'));
+
+  const authDir = path.join(projectRoot, 'store', 'auth');
+  const hasAuth =
+    fs.existsSync(authDir) &&
+    fs.readdirSync(authDir).length > 0;
+
+  let hasRegisteredGroups = false;
+  // Check JSON file first (pre-migration)
+  if (fs.existsSync(path.join(projectRoot, 'data', 'registered_groups.json'))) {
+    hasRegisteredGroups = true;
+  } else {
+    // Check SQLite directly using better-sqlite3 (no sqlite3 CLI needed)
+    const dbPath = path.join(STORE_DIR, 'messages.db');
+    if (fs.existsSync(dbPath)) {
+      try {
+        const db = new Database(dbPath, { readonly: true });
+        const row = db.prepare(
+          'SELECT COUNT(*) as count FROM registered_groups',
+        ).get() as { count: number };
+        if (row.count > 0) hasRegisteredGroups = true;
+        db.close();
+      } catch {
+        // Table might not exist yet
+      }
+    }
+  }
+
+  logger.info({ platform, wsl, appleContainer, docker, hasEnv, hasAuth, hasRegisteredGroups },
+    'Environment check complete');
+
+  emitStatus('CHECK_ENVIRONMENT', {
+    PLATFORM: platform,
+    IS_WSL: wsl,
+    IS_HEADLESS: headless,
+    APPLE_CONTAINER: appleContainer,
+    DOCKER: docker,
+    HAS_ENV: hasEnv,
+    HAS_AUTH: hasAuth,
+    HAS_REGISTERED_GROUPS: hasRegisteredGroups,
+    STATUS: 'success',
+    LOG: 'logs/setup.log',
+  });
+}