Close the remaining post-exit and control-path races by draining tail output with a quiet window plus a bounded final ready pass, and by returning consistent not-running errors after a process has already exited.
Add a dedicated helper binary and focused tests so the lifecycle behavior is reviewable on its own, and reject Windows disableTimeout requests that the buffered fallback cannot honor.
* Add an ability to stream stdin, stdout, and stderr
* Streaming of stdout and stderr has a configurable cap for total amount
of transmitted bytes (with an ability to disable it)
* Add support for overriding environment variables
* Add an ability to terminate running applications (using
`command/exec/terminate`)
* Add TTY/PTY support, with an ability to resize the terminal (using
`command/exec/resize`)
