## Summary
Starts the process of getting rid of `--full-auto`, with some
concessions:
1. Fully removes the command from the tui, since it just resolves to the
default permissions there, and encourages users to use the one-time
trust flow if they're not in a trusted repo.
2. Marks the command as deprecated in `codex exec`, in case users are
actively relying on this. We'll remove in an upcoming n+X release.
3. Cleans up some of the `codex sandbox` cli logic, to keep supporting
legacy sandbox policies for now.
This isn't the cleanest setup, but I think it is worthwhile to warn
users for one release before hard-removing it.
## Testing
- [x] Updated unit tests
## Why
`codex-rs/exec/src/lib.rs` already keeps unit tests in a sibling
`lib_tests.rs` module so the implementation stays top-heavy and easier
to read. This applies that same layout to the rest of
`codex-rs/exec/src` so each production file keeps its entry points and
helpers ahead of test code.
## What
- Move inline unit tests out of `cli.rs`, `main.rs`,
`event_processor_with_human_output.rs`, and
`event_processor_with_jsonl_output.rs` into sibling `*_tests.rs` files.
- Keep test modules wired through `#[cfg(test)]` plus `#[path = "..."]
mod tests;`, matching the `lib.rs` pattern.
- Preserve the existing test coverage and assertions while making this a
source-layout-only refactor.
## Verification
- `cargo test -p codex-exec`
