// Package execenv abstracts process execution so tool handlers (Bash,
// SubAgent fork, plugin sandboxing) can run against a local exec.Cmd in
// CLI / daemon mode or against a remote sandbox (E2B Firecracker, etc.)
// in SaaS mode. The Executor / Process pair is the sole injection point
// for "how do we actually run a child process" — everything above it
// calls these interfaces, nothing below assumes local fork.
//
// # API Consumption Shapes
//
// Both Executor and Process are form 3 (synchronous callback) under the
// three Flyto API shapes (see `docs/api-reference.md` "API 消费形态 /
// API Consumption Patterns"):
//
//   - Executor.Start: engine / tools call synchronously to launch a
//     child process; the backend implementation (local / sandbox)
//     returns a Process handle or error.
//   - Process.Wait / Kill / Stdin / Stdout / Stderr: synchronous method
//     calls on the returned handle, same shape.
//
// Package execenv 抽象进程执行: 工具处理器 (Bash / SubAgent fork / plugin
// 沙盒) 在 CLI / daemon 模式下跑本地 exec.Cmd, 在 SaaS 模式下跑远端沙盒
// (E2B Firecracker 等). Executor / Process 对是 "我们怎么真执行子进程" 的
// 唯一注入点 —— 上层都调这对接口, 下层不假设本地 fork.
//
// # API 消费形态
//
// Executor 和 Process 都是形态三 (同步回调, 见 `docs/api-reference.md`
// "API 消费形态 / API Consumption Patterns"):
//
//   - Executor.Start: 引擎 / 工具同步调启动子进程; 后端实现 (本地 / 沙盒)
//     返 Process 句柄或 error.
//   - Process.Wait / Kill / Stdin / Stdout / Stderr: 对返回句柄的同步方法调用, 同形态.
package execenv