fix(cli): address Gemini test report — local mode, validate bug, offline flag

A. acr init --local: new local mode, no Cloudflare account required;
   config defaults to mode:local when ~/.arcrun/config.yaml missing

B. validate node-count bug: removed faulty input/output node heuristic
   that dropped start/end nodes from config check; now all nodes except
   reserved 'input' keyword must have config entries

C. acr validate --offline: skip remote component-existence and credentials
   checks; local mode also auto-skips these checks

D. parts.ts: replace require('node:fs') with static import (ES module fix)

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

cli/src/commands/init.ts

@@ -4,7 +4,7 @@
  * 呼叫 arcrun.dev 取得 API Key，寫入 ~/.arcrun/config.yaml
  */
 import { createInterface } from 'node:readline/promises';
-import { writeFileSync, existsSync } from 'node:fs';
+import { writeFileSync, existsSync, readFileSync, appendFileSync } from 'node:fs';
 import { join } from 'node:path';
 import chalk from 'chalk';
 import { saveConfig, type ArcrunConfig } from '../lib/config.js';
@@ -16,13 +16,15 @@ async function prompt(rl: ReturnType<typeof createInterface>, question: string):
   return answer.trim();
 }
 
-export async function cmdInit(options: { selfHosted?: boolean }): Promise<void> {
+export async function cmdInit(options: { local?: boolean; selfHosted?: boolean }): Promise<void> {
   const rl = createInterface({ input: process.stdin, output: process.stdout });
 
   console.log(chalk.bold('\n  arcrun 初始化設定\n'));
 
   try {
-    if (options.selfHosted) {
+    if (options.local) {
+      await initLocal();
+    } else if (options.selfHosted) {
       await initSelfHosted(rl);
     } else {
       await initStandard(rl);
@@ -32,6 +34,24 @@ export async function cmdInit(options: { selfHosted?: boolean }): Promise<void>
   }
 }
 
+async function initLocal(): Promise<void> {
+  console.log(chalk.gray('  Local 模式：不需要 Cloudflare 帳號，直接在本機跑 workflow\n'));
+
+  const config: ArcrunConfig = {
+    mode: 'local',
+  };
+
+  saveConfig(config);
+  createCredentialsYamlIfMissing();
+
+  console.log(chalk.green('\n  ✓ 設定完成 → ~/.arcrun/config.yaml（local 模式）\n'));
+  console.log('  你可以立刻開始：');
+  console.log(chalk.cyan('    acr validate workflow.yaml --offline') + '  # 驗證 workflow 格式');
+  console.log(chalk.cyan('    acr run <workflow_name>') + '              # 本機執行\n');
+  console.log(chalk.gray('  Local 模式不連線 arcrun.dev，所有 workflow 在本機執行。'));
+  console.log(chalk.gray('  需要 Cloudflare 部署？執行 acr init（Standard 模式）。\n'));
+}
+
 async function initStandard(rl: ReturnType<typeof createInterface>): Promise<void> {
   console.log(chalk.gray('  Standard 模式：使用 arcrun.dev 的執行引擎，credential 存在你自己的 CF KV\n'));
 
@@ -137,7 +157,6 @@ function createCredentialsYamlIfMissing(): void {
   // 確保 .gitignore 排除 credentials.yaml
   const gitignorePath = join(process.cwd(), '.gitignore');
   if (existsSync(gitignorePath)) {
-    const { readFileSync, appendFileSync } = await import('node:fs');
     const content = readFileSync(gitignorePath, 'utf8');
     if (!content.includes('credentials.yaml')) {
       appendFileSync(gitignorePath, '\ncredentials.yaml\n');