Remove reasoning format (#8484)

This isn't very useful parameter. 

logic:
```
if model puts `**` in their reasoning, trim it and visualize the header.
if couldn't trim: don't render
if model doesn't support: don't render
```

We can simplify to:
```
if could trim, visualize header.
if not, don't render
```

codex-rs/tui/src/history_cell.rs

@@ -33,7 +33,6 @@ use codex_core::protocol::McpAuthStatus;
 use codex_core::protocol::McpInvocation;
 use codex_core::protocol::SessionConfiguredEvent;
 use codex_protocol::openai_models::ReasoningEffort as ReasoningEffortConfig;
-use codex_protocol::openai_models::ReasoningSummaryFormat;
 use codex_protocol::plan_tool::PlanItemArg;
 use codex_protocol::plan_tool::StepStatus;
 use codex_protocol::plan_tool::UpdatePlanArgs;
@@ -1661,39 +1660,28 @@ pub(crate) fn new_view_image_tool_call(path: PathBuf, cwd: &Path) -> PlainHistor
     PlainHistoryCell { lines }
 }
 
-pub(crate) fn new_reasoning_summary_block(
-    full_reasoning_buffer: String,
-    reasoning_summary_format: ReasoningSummaryFormat,
-) -> Box<dyn HistoryCell> {
-    if reasoning_summary_format == ReasoningSummaryFormat::Experimental {
-        // Experimental format is following:
-        // ** header **
-        //
-        // reasoning summary
-        //
-        // So we need to strip header from reasoning summary
-        let full_reasoning_buffer = full_reasoning_buffer.trim();
-        if let Some(open) = full_reasoning_buffer.find("**") {
-            let after_open = &full_reasoning_buffer[(open + 2)..];
-            if let Some(close) = after_open.find("**") {
-                let after_close_idx = open + 2 + close + 2;
-                // if we don't have anything beyond `after_close_idx`
-                // then we don't have a summary to inject into history
-                if after_close_idx < full_reasoning_buffer.len() {
-                    let header_buffer = full_reasoning_buffer[..after_close_idx].to_string();
-                    let summary_buffer = full_reasoning_buffer[after_close_idx..].to_string();
-                    return Box::new(ReasoningSummaryCell::new(
-                        header_buffer,
-                        summary_buffer,
-                        false,
-                    ));
-                }
+pub(crate) fn new_reasoning_summary_block(full_reasoning_buffer: String) -> Box<dyn HistoryCell> {
+    let full_reasoning_buffer = full_reasoning_buffer.trim();
+    if let Some(open) = full_reasoning_buffer.find("**") {
+        let after_open = &full_reasoning_buffer[(open + 2)..];
+        if let Some(close) = after_open.find("**") {
+            let after_close_idx = open + 2 + close + 2;
+            // if we don't have anything beyond `after_close_idx`
+            // then we don't have a summary to inject into history
+            if after_close_idx < full_reasoning_buffer.len() {
+                let header_buffer = full_reasoning_buffer[..after_close_idx].to_string();
+                let summary_buffer = full_reasoning_buffer[after_close_idx..].to_string();
+                return Box::new(ReasoningSummaryCell::new(
+                    header_buffer,
+                    summary_buffer,
+                    false,
+                ));
             }
         }
     }
     Box::new(ReasoningSummaryCell::new(
         "".to_string(),
-        full_reasoning_buffer,
+        full_reasoning_buffer.to_string(),
         true,
     ))
 }
@@ -1759,7 +1747,6 @@ mod tests {
     use codex_core::config::ConfigBuilder;
     use codex_core::config::types::McpServerConfig;
     use codex_core::config::types::McpServerTransportConfig;
-    use codex_core::models_manager::manager::ModelsManager;
     use codex_core::protocol::McpAuthStatus;
     use codex_protocol::parse_command::ParsedCommand;
     use dirs::home_dir;
@@ -2672,10 +2659,8 @@ mod tests {
     }
     #[test]
     fn reasoning_summary_block() {
-        let reasoning_format = ReasoningSummaryFormat::Experimental;
         let cell = new_reasoning_summary_block(
             "**High level reasoning**\n\nDetailed reasoning goes here.".to_string(),
-            reasoning_format,
         );
 
         let rendered_display = render_lines(&cell.display_lines(80));
@@ -2687,11 +2672,7 @@ mod tests {
 
     #[test]
     fn reasoning_summary_block_returns_reasoning_cell_when_feature_disabled() {
-        let reasoning_format = ReasoningSummaryFormat::Experimental;
-        let cell = new_reasoning_summary_block(
-            "Detailed reasoning goes here.".to_string(),
-            reasoning_format,
-        );
+        let cell = new_reasoning_summary_block("Detailed reasoning goes here.".to_string());
 
         let rendered = render_transcript(cell.as_ref());
         assert_eq!(rendered, vec!["• Detailed reasoning goes here."]);
@@ -2702,17 +2683,8 @@ mod tests {
         let mut config = test_config().await;
         config.model = Some("gpt-3.5-turbo".to_string());
         config.model_supports_reasoning_summaries = Some(true);
-        config.model_reasoning_summary_format = Some(ReasoningSummaryFormat::Experimental);
-        let model_family =
-            ModelsManager::construct_model_family_offline(&config.model.clone().unwrap(), &config);
-        assert_eq!(
-            model_family.reasoning_summary_format,
-            ReasoningSummaryFormat::Experimental
-        );
-
         let cell = new_reasoning_summary_block(
             "**High level reasoning**\n\nDetailed reasoning goes here.".to_string(),
-            model_family.reasoning_summary_format,
         );
 
         let rendered_display = render_lines(&cell.display_lines(80));
@@ -2721,11 +2693,8 @@ mod tests {
 
     #[test]
     fn reasoning_summary_block_falls_back_when_header_is_missing() {
-        let reasoning_format = ReasoningSummaryFormat::Experimental;
-        let cell = new_reasoning_summary_block(
-            "**High level reasoning without closing".to_string(),
-            reasoning_format,
-        );
+        let cell =
+            new_reasoning_summary_block("**High level reasoning without closing".to_string());
 
         let rendered = render_transcript(cell.as_ref());
         assert_eq!(rendered, vec!["• **High level reasoning without closing"]);
@@ -2733,18 +2702,14 @@ mod tests {
 
     #[test]
     fn reasoning_summary_block_falls_back_when_summary_is_missing() {
-        let reasoning_format = ReasoningSummaryFormat::Experimental;
-        let cell = new_reasoning_summary_block(
-            "**High level reasoning without closing**".to_string(),
-            reasoning_format.clone(),
-        );
+        let cell =
+            new_reasoning_summary_block("**High level reasoning without closing**".to_string());
 
         let rendered = render_transcript(cell.as_ref());
         assert_eq!(rendered, vec!["• High level reasoning without closing"]);
 
         let cell = new_reasoning_summary_block(
             "**High level reasoning without closing**\n\n  ".to_string(),
-            reasoning_format,
         );
 
         let rendered = render_transcript(cell.as_ref());
@@ -2753,10 +2718,8 @@ mod tests {
 
     #[test]
     fn reasoning_summary_block_splits_header_and_summary_when_present() {
-        let reasoning_format = ReasoningSummaryFormat::Experimental;
         let cell = new_reasoning_summary_block(
             "**High level plan**\n\nWe should fix the bug next.".to_string(),
-            reasoning_format,
         );
 
         let rendered_display = render_lines(&cell.display_lines(80));