Byte truncation doesn't preserve command output tails, confusing codex (e.g. with cargo output)

What version of Codex is running?

main (a47181e471b6efe55e95f9858c913fc89a3a44fa)

What subscription do you have?

pro

Which model were you using?

_No response_

What platform is your computer?

_No response_

What issue are you seeing?

When running commands that have few lines but long lines, byte truncation kicks in instead of line truncation.

A good example of this can be cargo run, emitting a combination of build and log output.

Line truncation preserves both head and tail, but byte truncation currently cuts off the end of output.

This totally confuses codex, which will (for example) run a cargo build that _fails_, but interpret it as having succeeded (because it sees no errors in the output.

What steps can reproduce the bug?

Run any command that has few but long lines, causing byte truncation to kick in.

What is the expected behavior?

Byte truncation should – like line truncation – preserve both head and tail portions of the command output (as in this commit).

Additional information

_No response_