## 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
Addresses #18113
Problem: Shared flags provided before the exec subcommand were parsed by
the root CLI but not inherited by the exec CLI, so exec sessions could
run with stale or default sandbox and model configuration.
Solution: Move shared TUI and exec flags into a common option block and
merge root selections into exec before dispatch, while preserving exec's
global subcommand flag behavior.
