docs(exec): add exec command to AGENTS.md

Author: fengmk2

packages/cli/AGENTS.md

@@ -18,6 +18,7 @@ This project is using Vite+, a modern toolchain built on top of Vite, Rolldown,
 - lib - Build library
 - migrate - Migrate an existing project to Vite+
 - new - Create a new monorepo package (in-project) or a new project (global)
+- exec - Execute a command in workspace packages (supports `--filter`, `-r`, `--parallel`)
 - run - Run tasks from `package.json` scripts
 
 These commands map to their corresponding tools. For example, `vp dev --port 3000` runs Vite's dev server and works the same as Vite. `vp test` runs JavaScript tests through the bundled Vitest. The version of all tools can be checked using `vp --version`. This is useful when researching documentation, features, and bugs.