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/index.ts

@@ -27,8 +27,9 @@ program
 program
   .command('init')
   .description('互動式初始化設定（建立 ~/.arcrun/config.yaml）')
-  .option('--self-hosted', '使用 Self-hosted 模式（自行部署所有 Worker）')
-  .action((options: { selfHosted?: boolean }) => cmdInit(options));
+  .option('--local', '本機模式：不需要 Cloudflare 帳號，直接在本機測試 workflow')
+  .option('--self-hosted', '完全 Self-hosted 模式：自行部署所有 Cloudflare Worker')
+  .action((options: { local?: boolean; selfHosted?: boolean }) => cmdInit(options));
 
 // acr creds push [credentials.yaml]
 const credsCmd = program.command('creds').description('Credential 管理');
@@ -54,7 +55,8 @@ program
 program
   .command('validate <file>')
   .description('執行前驗證 workflow.yaml（格式、關係詞、零件存在性、credentials）')
-  .action((file: string) => cmdValidate(file));
+  .option('--offline', '離線模式：跳過零件存在性與 credentials 的遠端檢查')
+  .action((file: string, options: { offline?: boolean }) => cmdValidate(file, options));
 
 // acr parts
 // acr parts scaffold <component>