Add timestamp to header printed at end-of-turn output.

What variant of Codex are you using?

CLI

What feature would you like to see?

At the end of a turn there will sometimes be a header printing the wall clock time for the turn. For example:

─ Worked for 1m 23s ────────────────────────────────────────────────────────────────────────────────────────────────────

It would be useful to include a timestamp in that output line. For the use case of working with multiple sessions in tmux the timestamp can give information to the user on when the session was last running.

Additional information

Potentially relevant: #5148

Tested against:

$ codex --version
codex-cli 0.114.0
$ uname -mrsv
OpenBSD 7.8 GENERIC.MP#4 amd64

WIth Port from https://github.com/DeciSym/openbsd-port-codex.