refactor: migrate CLI from packages/server to apps/cli

Move the CLI application from packages/server/ to apps/cli/ to align
with the monorepo convention (apps/ for deployable applications,
packages/ for shared libraries). Rename package to @openchatlab/chatlab.

Also fix a bug in ensureToken() that used raw string manipulation to
write config.toml, causing duplicate token fields that corrupted the
TOML file. This led to config parse failures and user_data_dir being
overwritten with defaults. Now uses writeConfigField() for safe writes.

apps/cli/bin/chatlab.js

@@ -0,0 +1,13 @@
+#!/usr/bin/env node
+
+/**
+ * ChatLab CLI 入口
+ *
+ * 开发阶段：通过 pnpm --filter chatlab dev 运行（使用 tsx）
+ * 发布阶段：构建后直接作为 Node.js 脚本运行
+ */
+
+// 开发阶段占位，实际通过 package.json scripts 的 tsx 运行
+console.error('Please run via: npx tsx apps/cli/src/cli.ts')
+console.error('Or use: pnpm --filter @openchatlab/chatlab cli')
+process.exit(1)