chore: Clean up verbosity config (#3056)

## Summary
It appears that #2108 hit a merge conflict with #2355 - I failed to
notice the path difference when re-reviewing the former. This PR
rectifies that, and consolidates it into the protocol package, in line
with our philosophy of specifying types in one place.

## Testing
- [x] Adds config test for model_verbosity

codex-rs/core/src/config_profile.rs

@@ -1,10 +1,10 @@
 use serde::Deserialize;
 use std::path::PathBuf;
 
-use crate::config_types::Verbosity;
 use crate::protocol::AskForApproval;
 use codex_protocol::config_types::ReasoningEffort;
 use codex_protocol::config_types::ReasoningSummary;
+use codex_protocol::config_types::Verbosity;
 
 /// Collection of common configuration options that a user can define as a unit
 /// in `config.toml`.