Honor pager bindings for transcript page keys (#50396)

## Why

Transcript scrolling hardcoded `PageUp` and `PageDown` to full-page movement, ignoring customized pager bindings.

## What changed

Resolve unmodified `PageUp` and `PageDown` through the pager's scroll bindings so they can scroll by a full page, half a page, or one row, or remain unbound. Preserve the one-row overlap for full-page scrolling and leave pager typing shortcuts unhandled by the transcript.

## Testing

Add a regression test and snapshot covering default, half-page, single-row, and unbound configurations. Verify that `PageDown` reverses `PageUp` scrolling and that `j` and `Ctrl+u` remain unhandled.

GitOrigin-RevId: 945e99d7370f84f326ab71037be2924dddada32c

codex-rs/tui/src/snapshots/codex_tui__transcript_view__tests__page_keys_follow_pager_scroll_bindings.snap

@@ -0,0 +1,43 @@
+---
+source: tui/src/transcript_view_tests.rs
+expression: "frames.join(\"\\n\\n\")"
+---
+default
+row 16
+row 17
+row 18
+row 19
+row 20
+row 21
+row 22
+row 23
+
+half page
+row 19
+row 20
+row 21
+row 22
+row 23
+row 24
+row 25
+row 26
+
+single row
+row 22
+row 23
+row 24
+row 25
+row 26
+row 27
+row 28
+row 29
+
+unbound
+row 23
+row 24
+row 25
+row 26
+row 27
+row 28
+row 29
+row 30

codex-rs/tui/src/transcript_view/input.rs

@@ -343,17 +343,24 @@ impl TranscriptView {
     ) -> Option<ViewAction> {
         let jump = JumpTarget::from_key(key);
         match (key.code, key.modifiers) {
-            (KeyCode::PageUp, KeyModifiers::NONE) => {
-                self.scroll(
-                    cells,
-                    -(self.area.height.saturating_sub(/*rhs*/ 1).max(/*other*/ 1) as isize),
-                );
-            }
-            (KeyCode::PageDown, KeyModifiers::NONE) => {
-                self.scroll(
-                    cells,
-                    self.area.height.saturating_sub(/*rhs*/ 1).max(/*other*/ 1) as isize,
-                );
+            (KeyCode::PageUp | KeyCode::PageDown, KeyModifiers::NONE) => {
+                // Share page-key configuration without taking the pager's typing shortcuts.
+                // Full pages retain the main view's existing one-row overlap.
+                let keymap = &self.disclosure.keymap.pager;
+                let height = self.area.height.max(/*other*/ 1) as isize;
+                let page = (height - 1).max(/*other*/ 1);
+                let half = (height + 1) / 2;
+                let delta = [
+                    (&keymap.scroll_up, -1),
+                    (&keymap.scroll_down, 1),
+                    (&keymap.page_up, -page),
+                    (&keymap.page_down, page),
+                    (&keymap.half_page_up, -half),
+                    (&keymap.half_page_down, half),
+                ]
+                .into_iter()
+                .find_map(|(bindings, delta)| bindings.is_pressed(key).then_some(delta))?;
+                self.scroll(cells, delta);
             }
             (KeyCode::Esc, KeyModifiers::NONE) if self.can_return_to_latest() => {
                 self.jump_to_latest();

codex-rs/tui/src/transcript_view_tests.rs

@@ -63,6 +63,77 @@ pub(super) fn text(buffer: &Buffer) -> String {
         .join("\n")
 }
 
+#[test]
+fn page_keys_follow_pager_scroll_bindings() {
+    let cells = [cell(
+        (1..=30)
+            .map(|row| format!("row {row}\n"))
+            .collect::<String>(),
+    )];
+    let mut frames = Vec::new();
+    for (label, pager, rows) in [
+        ("default", serde_json::json!({}), 7),
+        (
+            "half page",
+            serde_json::json!({
+                "page_up": [], "page_down": [],
+                "half_page_up": "page-up", "half_page_down": "page-down"
+            }),
+            4,
+        ),
+        (
+            "single row",
+            serde_json::json!({
+                "page_up": [], "page_down": [],
+                "scroll_up": "page-up", "scroll_down": "page-down"
+            }),
+            1,
+        ),
+        (
+            "unbound",
+            serde_json::json!({"page_up": [], "page_down": []}),
+            0,
+        ),
+    ] {
+        let config = serde_json::from_value(serde_json::json!({"pager": pager})).unwrap();
+        let keymap = crate::keymap::RuntimeKeymap::from_config(&config).unwrap();
+        let mut view = TranscriptView::default();
+        view.set_keymap_bindings(&keymap);
+        let pre_scroll = render(&mut view, &cells, /*width*/ 20, /*height*/ 8);
+        assert_eq!(
+            view.handle_key(KeyCode::PageUp.into(), &cells).is_some(),
+            rows != 0
+        );
+        let scrolled = render(&mut view, &cells, /*width*/ 20, /*height*/ 8);
+        let mut expected = TranscriptView::default();
+        render(&mut expected, &cells, /*width*/ 20, /*height*/ 8);
+        expected.scroll(&cells, -rows);
+        assert_eq!(
+            scrolled,
+            render(&mut expected, &cells, /*width*/ 20, /*height*/ 8)
+        );
+        frames.push(format!("{label}\n{}", text(&scrolled)));
+        assert_eq!(
+            view.handle_key(KeyCode::PageDown.into(), &cells).is_some(),
+            rows != 0
+        );
+        assert_eq!(
+            render(&mut view, &cells, /*width*/ 20, /*height*/ 8),
+            pre_scroll
+        );
+        for key in [
+            KeyCode::Char('j').into(),
+            KeyEvent::new(KeyCode::Char('u'), KeyModifiers::CONTROL),
+        ] {
+            assert!(view.handle_key(key, &cells).is_none());
+        }
+    }
+    insta::assert_snapshot!(
+        "page_keys_follow_pager_scroll_bindings",
+        frames.join("\n\n")
+    );
+}
+
 #[test]
 fn terminal_output_disclosure_follows_live_history_and_keymap() {
     use crate::exec_cell::CommandOutput;