Allow transcript selection and copying while bottom modals are open (#50564)

## Why

The plan confirmation prompt allowed transcript scrolling but blocked selecting and copying the visible plan text.

## What changed

Allow mouse selection and copying in the visible transcript while a bottom modal is open, preserving drags across redraws. Keep other keyboard input with the modal and suppress transcript link activation, disclosure toggles, and follow-control clicks during modal mouse handling.

## Testing

Extend the plan prompt test to cover selection, `Ctrl+Insert` copying, selection highlighting, and popup bounds. Add coverage confirming that ordinary and Control-clicks do not open links in selection-only mouse handling.

GitOrigin-RevId: 9e1fdfcb4bc18215e62a714f173bc8cb372b090a

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

@@ -306,6 +306,38 @@ fn ordinary_click_opens_bare_and_markdown_links_on_release() {
     }
 }
 
+#[test]
+fn selection_mouse_does_not_open_links() {
+    for modifiers in [KeyModifiers::NONE, KeyModifiers::CONTROL] {
+        let (mut view, cells) = transcript("[docs](https://example.com/docs)", /*width*/ 60);
+        let down = MouseEvent {
+            modifiers,
+            ..mouse(
+                MouseEventKind::Down(MouseButton::Left),
+                /*column*/ 4,
+                /*row*/ 1,
+            )
+        };
+        assert!(matches!(
+            view.handle_selection_mouse(down, &cells),
+            Some(ViewAction::Changed)
+        ));
+        let area = view.area;
+        view.render(area, &mut Buffer::empty(area), &cells);
+        assert!(matches!(
+            view.handle_selection_mouse(
+                MouseEvent {
+                    kind: MouseEventKind::Up(MouseButton::Left),
+                    ..down
+                },
+                &cells,
+            ),
+            Some(ViewAction::Changed)
+        ));
+        assert_eq!(view.selected_text(&cells), None);
+    }
+}
+
 #[test]
 fn dragging_a_link_selects_text_and_never_opens_it() {
     for return_to_origin in [false, true] {