fix: 修复 /agents/commands 接口 duplicate command name 和返回多余 TUI 命令

1. cost/index.ts 重导出 usage/index.ts，COMMANDS() 中移除 cost 避免 BuildManifest 重复校验
2. /command 端点只返回 prompt 类型的 skills 命令，排除 TUI 命令

Co-Authored-By: DeepSeek-V4-Pro-VIP <deepseek-ai@claude-code-best.win>

src/commands.ts

@@ -314,7 +314,7 @@ const COMMANDS = memoize((): Command[] => [
   // desktop,
   context,
   contextNonInteractive,
-  cost,
+  // cost 已重导出 usage/index.ts（name='usage', aliases=['cost','stats']），
   diff,
   doctor,
   effort,

src/server/routes/info.ts

@@ -32,7 +32,7 @@ export function createInfoRoutes(sessionManager: SessionManager): Hono {
         const commands = await getCommands(process.cwd())
         return c.json(
           commands
-            .filter(cmd => !cmd.isHidden)
+            .filter(cmd => !cmd.isHidden && cmd.type === 'prompt')
             .map(cmd => ({
               name: getCommandName(cmd),
               description: cmd.description,