app-server: Add streaming and tty/pty capabilities to command/exec (#13640)

* 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`)

codex-rs/app-server-test-client/src/lib.rs

@@ -96,6 +96,7 @@ const NOTIFICATIONS_TO_OPT_OUT: &[&str] = &[
     "codex/event/item_started",
     "codex/event/item_completed",
     // v2 item deltas.
+    "command/exec/outputDelta",
     "item/agentMessage/delta",
     "item/plan/delta",
     "item/commandExecution/outputDelta",