Rename tui_app_server to tui (#16104)

This is a follow-up to https://github.com/openai/codex/pull/15922. That
previous PR deleted the old `tui` directory and left the new
`tui_app_server` directory in place. This PR renames `tui_app_server` to
`tui` and fixes up all references.

codex-rs/tui/tests/suite/vt100_live_commit.rs

@@ -0,0 +1,45 @@
+#![cfg(feature = "vt100-tests")]
+
+use crate::test_backend::VT100Backend;
+use ratatui::layout::Rect;
+use ratatui::text::Line;
+
+#[test]
+fn live_001_commit_on_overflow() {
+    let backend = VT100Backend::new(20, 6);
+    let mut term = match codex_tui::custom_terminal::Terminal::with_options(backend) {
+        Ok(t) => t,
+        Err(e) => panic!("failed to construct terminal: {e}"),
+    };
+    let area = Rect::new(0, 5, 20, 1);
+    term.set_viewport_area(area);
+
+    // Build 5 explicit rows at width 20.
+    let mut rb = codex_tui::live_wrap::RowBuilder::new(20);
+    rb.push_fragment("one\n");
+    rb.push_fragment("two\n");
+    rb.push_fragment("three\n");
+    rb.push_fragment("four\n");
+    rb.push_fragment("five\n");
+
+    // Keep the last 3 in the live ring; commit the first 2.
+    let commit_rows = rb.drain_commit_ready(3);
+    let lines: Vec<Line<'static>> = commit_rows.into_iter().map(|r| r.text.into()).collect();
+
+    codex_tui::insert_history::insert_history_lines(&mut term, lines)
+        .expect("Failed to insert history lines in test");
+
+    let screen = term.backend().vt100().screen();
+
+    // The words "one" and "two" should appear above the viewport.
+    let joined = screen.contents();
+    assert!(
+        joined.contains("one"),
+        "expected committed 'one' to be visible\n{joined}"
+    );
+    assert!(
+        joined.contains("two"),
+        "expected committed 'two' to be visible\n{joined}"
+    );
+    // The last three (three,four,five) remain in the live ring, not committed here.
+}