When I originally wrote `elapsed.rs`, I realized we were using both `std::time` and `chrono` with no real benefit of having both. We should try to keep the `exec` subcommand trim (as it also buildable as a standalone executable), so this helps tighten things up.
codex-common
This crate is designed for utilities that need to be shared across other crates in the workspace, but should not go in core.
For narrow utility features, the pattern is to add introduce a new feature under [features] in Cargo.toml and then gate it with #[cfg] in lib.rs, as appropriate.