Clamp session headers to narrow terminal widths (#34775)

## Why

Session header rows can exceed the available inner width when the terminal is
narrow, causing the bordered header to render wider than its requested width.

## What changed

Truncate each session header row to the available inner width and append an
ellipsis when content overflows.

## Testing

Add a snapshot test for a 44-column session header and assert that every
rendered line matches the requested width.

GitOrigin-RevId: 7cf0ea48aa95a6f1ddd1a9dbb7c7fb70bdbcb5a3

codex-rs/tui/src/history_cell/session.rs

@@ -1,6 +1,7 @@
 //! Session headers, onboarding guidance, and transcript cards.
 
 use super::*;
+use crate::line_truncation::truncate_line_with_ellipsis_if_overflow;
 
 pub(crate) const SESSION_HEADER_MAX_INNER_WIDTH: usize = 56; // Just an eyeballed value
 
@@ -390,6 +391,10 @@ impl HistoryCell for SessionHeaderHistoryCell {
             ]));
         }
 
+        let lines = lines
+            .into_iter()
+            .map(|line| truncate_line_with_ellipsis_if_overflow(line, inner_width))
+            .collect();
         with_border(lines)
     }
 

codex-rs/tui/src/history_cell/snapshots/codex_tui__history_cell__tests__session_header_clamps_to_narrow_width.snap

@@ -0,0 +1,11 @@
+---
+source: tui/src/history_cell/tests.rs
+expression: "render_lines(&lines).join(\"\\n\")"
+---
+╭──────────────────────────────────────────╮
+│ >_ OpenAI Codex (vtest)                  │
+│                                          │
+│ model:       gpt-5.6-sol xhigh   fast  … │
+│ directory:   project                     │
+│ permissions: YOLO mode                   │
+╰──────────────────────────────────────────╯

codex-rs/tui/src/history_cell/tests.rs

@@ -6,6 +6,7 @@ use crate::exec_cell::ExecCall;
 use crate::exec_cell::ExecCell;
 use crate::legacy_core::config::Config;
 use crate::legacy_core::config::ConfigBuilder;
+use crate::line_truncation::line_width;
 use crate::session_state::ThreadSessionState;
 use crate::wrapping::word_wrap_lines;
 use codex_app_server_protocol::AskForApproval;
@@ -1568,6 +1569,25 @@ fn session_header_hides_fast_status_when_disabled() {
     assert!(!model_line.contains("fast"));
 }
 
+#[test]
+fn session_header_clamps_to_narrow_width() {
+    const WIDTH: u16 = 44;
+    let cell = SessionHeaderHistoryCell::new(
+        "gpt-5.6-sol".to_string(),
+        Some(ReasoningEffortConfig::XHigh),
+        /*show_fast_status*/ true,
+        PathBuf::from("project"),
+        "test",
+    )
+    .with_yolo_mode(/*yolo_mode*/ true);
+
+    let lines = cell.display_lines(WIDTH);
+    let widths = lines.iter().map(line_width).collect::<Vec<_>>();
+
+    assert_eq!(widths, vec![usize::from(WIDTH); lines.len()]);
+    insta::assert_snapshot!(render_lines(&lines).join("\n"));
+}
+
 #[test]
 #[cfg_attr(
     target_os = "windows",