[tui] Show speed in session header (#13446)

- add a speed row to the startup/session header under the model row
- render the speed row with the same styling pattern as the model row,
using /fast to change
- show only Fast or Standard to users and update the affected snapshots

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/tui/src/chatwidget.rs

@@ -1224,6 +1224,7 @@ impl ChatWidget {
         self.sync_fast_command_enabled();
         self.sync_personality_command_enabled();
         let startup_tooltip_override = self.startup_tooltip_override.take();
+        let show_fast_status = self.should_show_fast_status(event.service_tier);
         let session_info_cell = history_cell::new_session_info(
             &self.config,
             &model_for_header,
@@ -1233,6 +1234,7 @@ impl ChatWidget {
             self.auth_manager
                 .auth_cached()
                 .and_then(|auth| auth.account_plan_type()),
+            show_fast_status,
         );
         self.apply_session_info_cell(session_info_cell);
 
@@ -7221,6 +7223,15 @@ impl ChatWidget {
         self.config.service_tier
     }
 
+    pub(crate) fn should_show_fast_status(&self, service_tier: Option<ServiceTier>) -> bool {
+        matches!(service_tier, Some(ServiceTier::Fast))
+            && self
+                .auth_manager
+                .auth_cached()
+                .as_ref()
+                .is_some_and(CodexAuth::is_chatgpt_auth)
+    }
+
     fn fast_mode_enabled(&self) -> bool {
         self.config.features.enabled(Feature::FastMode)
     }
@@ -7555,6 +7566,7 @@ impl ChatWidget {
             DEFAULT_MODEL_DISPLAY_NAME.to_string(),
             placeholder_style,
             None,
+            false,
             config.cwd.clone(),
             CODEX_CLI_VERSION,
         ))