## Why
`codex features list` currently prints features in declaration order
from `codex_core::features::FEATURES`. That makes the output harder to
scan when looking for a specific flag, and the order can change for
reasons unrelated to the CLI.
## What changed
- Sort the `codex features list` rows by feature key before printing
them in `codex-rs/cli/src/main.rs`.
- Add an integration test in `codex-rs/cli/tests/features.rs` that runs
`codex features list` and asserts the feature-name column is
alphabetized.
## Verification
- Added `features_list_is_sorted_alphabetically_by_feature_name`.
- Ran `cargo test -p codex-cli`.
## Summary
- add `codex features enable <feature>` and `codex features disable
<feature>`
- persist feature flag changes to `config.toml` (respecting profile)
- print the under-development feature warning when enabling prerelease
features
- keep `features list` behavior unchanged and add unit/integration tests
## Testing
- cargo test -p codex-cli
