feat(tui2): copy tui crate and normalize snapshots (#7833)

Introduce a full codex-tui source snapshot under the new codex-tui2
crate so viewport work can be replayed in isolation.

This change copies the entire codex-rs/tui/src tree into
codex-rs/tui2/src in one atomic step, rather than piecemeal, to keep
future diffs vs the original viewport bookmark easy to reason about.

The goal is for codex-tui2 to render identically to the existing TUI
behind the `features.tui2` flag while we gradually port the
viewport/history commits from the joshka/viewport bookmark onto this
forked tree.

While on this baseline change, we also ran the codex-tui2 snapshot test
suite and accepted all insta snapshots for the new crate, so the
snapshot files now use the codex-tui2 naming scheme and encode the
unmodified legacy TUI behavior. This keeps later viewport commits
focused on intentional behavior changes (and their snapshots) rather
than on mechanical snapshot renames.

codex-rs/tui2/src/key_hint.rs

@@ -0,0 +1,112 @@
+use crossterm::event::KeyCode;
+use crossterm::event::KeyEvent;
+use crossterm::event::KeyEventKind;
+use crossterm::event::KeyModifiers;
+use ratatui::style::Style;
+use ratatui::style::Stylize;
+use ratatui::text::Span;
+
+#[cfg(test)]
+const ALT_PREFIX: &str = "⌥ + ";
+#[cfg(all(not(test), target_os = "macos"))]
+const ALT_PREFIX: &str = "⌥ + ";
+#[cfg(all(not(test), not(target_os = "macos")))]
+const ALT_PREFIX: &str = "alt + ";
+const CTRL_PREFIX: &str = "ctrl + ";
+const SHIFT_PREFIX: &str = "shift + ";
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub(crate) struct KeyBinding {
+    key: KeyCode,
+    modifiers: KeyModifiers,
+}
+
+impl KeyBinding {
+    pub(crate) const fn new(key: KeyCode, modifiers: KeyModifiers) -> Self {
+        Self { key, modifiers }
+    }
+
+    pub fn is_press(&self, event: KeyEvent) -> bool {
+        self.key == event.code
+            && self.modifiers == event.modifiers
+            && (event.kind == KeyEventKind::Press || event.kind == KeyEventKind::Repeat)
+    }
+}
+
+pub(crate) const fn plain(key: KeyCode) -> KeyBinding {
+    KeyBinding::new(key, KeyModifiers::NONE)
+}
+
+pub(crate) const fn alt(key: KeyCode) -> KeyBinding {
+    KeyBinding::new(key, KeyModifiers::ALT)
+}
+
+pub(crate) const fn shift(key: KeyCode) -> KeyBinding {
+    KeyBinding::new(key, KeyModifiers::SHIFT)
+}
+
+pub(crate) const fn ctrl(key: KeyCode) -> KeyBinding {
+    KeyBinding::new(key, KeyModifiers::CONTROL)
+}
+
+pub(crate) const fn ctrl_alt(key: KeyCode) -> KeyBinding {
+    KeyBinding::new(key, KeyModifiers::CONTROL.union(KeyModifiers::ALT))
+}
+
+fn modifiers_to_string(modifiers: KeyModifiers) -> String {
+    let mut result = String::new();
+    if modifiers.contains(KeyModifiers::CONTROL) {
+        result.push_str(CTRL_PREFIX);
+    }
+    if modifiers.contains(KeyModifiers::SHIFT) {
+        result.push_str(SHIFT_PREFIX);
+    }
+    if modifiers.contains(KeyModifiers::ALT) {
+        result.push_str(ALT_PREFIX);
+    }
+    result
+}
+
+impl From<KeyBinding> for Span<'static> {
+    fn from(binding: KeyBinding) -> Self {
+        (&binding).into()
+    }
+}
+impl From<&KeyBinding> for Span<'static> {
+    fn from(binding: &KeyBinding) -> Self {
+        let KeyBinding { key, modifiers } = binding;
+        let modifiers = modifiers_to_string(*modifiers);
+        let key = match key {
+            KeyCode::Enter => "enter".to_string(),
+            KeyCode::Char(' ') => "space".to_string(),
+            KeyCode::Up => "↑".to_string(),
+            KeyCode::Down => "↓".to_string(),
+            KeyCode::Left => "←".to_string(),
+            KeyCode::Right => "→".to_string(),
+            KeyCode::PageUp => "pgup".to_string(),
+            KeyCode::PageDown => "pgdn".to_string(),
+            _ => format!("{key}").to_ascii_lowercase(),
+        };
+        Span::styled(format!("{modifiers}{key}"), key_hint_style())
+    }
+}
+
+fn key_hint_style() -> Style {
+    Style::default().dim()
+}
+
+pub(crate) fn has_ctrl_or_alt(mods: KeyModifiers) -> bool {
+    (mods.contains(KeyModifiers::CONTROL) || mods.contains(KeyModifiers::ALT)) && !is_altgr(mods)
+}
+
+#[cfg(windows)]
+#[inline]
+pub(crate) fn is_altgr(mods: KeyModifiers) -> bool {
+    mods.contains(KeyModifiers::ALT) && mods.contains(KeyModifiers::CONTROL)
+}
+
+#[cfg(not(windows))]
+#[inline]
+pub(crate) fn is_altgr(_mods: KeyModifiers) -> bool {
+    false
+}