feat(tui) /personality (#9718)

## Summary
Adds /personality selector in the TUI, which leverages the new core
interface in #9644

Notes:
- We are doing some of our own state management for model_info loading
here, but not sure if that's ideal. open to opinions on simpler
approach, but would like to avoid blocking on a larger refactor
- Right now, the `/personality` selector just hides when the model
doesn't support it. we can update this behavior down the line

## Testing
- [x] Tested locally
- [x] Added snapshot tests

codex-rs/core/src/config/edit.rs

@@ -4,6 +4,7 @@ use crate::config::types::Notice;
 use crate::path_utils::resolve_symlink_write_paths;
 use crate::path_utils::write_atomically;
 use anyhow::Context;
+use codex_protocol::config_types::Personality;
 use codex_protocol::config_types::TrustLevel;
 use codex_protocol::openai_models::ReasoningEffort;
 use std::collections::BTreeMap;
@@ -24,6 +25,8 @@ pub enum ConfigEdit {
         model: Option<String>,
         effort: Option<ReasoningEffort>,
     },
+    /// Update the active (or default) model personality.
+    SetModelPersonality { personality: Option<Personality> },
     /// Toggle the acknowledgement flag under `[notice]`.
     SetNoticeHideFullAccessWarning(bool),
     /// Toggle the Windows world-writable directories warning acknowledgement flag.
@@ -269,6 +272,10 @@ impl ConfigDocument {
                 );
                 mutated
             }),
+            ConfigEdit::SetModelPersonality { personality } => Ok(self.write_profile_value(
+                &["model_personality"],
+                personality.map(|personality| value(personality.to_string())),
+            )),
             ConfigEdit::SetNoticeHideFullAccessWarning(acknowledged) => Ok(self.write_value(
                 Scope::Global,
                 &[Notice::TABLE_KEY, "hide_full_access_warning"],
@@ -712,6 +719,12 @@ impl ConfigEditsBuilder {
         self
     }
 
+    pub fn set_model_personality(mut self, personality: Option<Personality>) -> Self {
+        self.edits
+            .push(ConfigEdit::SetModelPersonality { personality });
+        self
+    }
+
     pub fn set_hide_full_access_warning(mut self, acknowledged: bool) -> Self {
         self.edits
             .push(ConfigEdit::SetNoticeHideFullAccessWarning(acknowledged));