Fix jitter in TUI apps/connectors picker (#10593)

This PR fixes jitter in the TUI apps menu by making the description
column stable during rendering and height measurement.
Added a `stable_desc_col` option to
`SelectionViewParams`/`ListSelectionView`, introduced stable variants of
the shared row render/measure helpers in `selection_popup_common`, and
enabled the stable mode for the apps/connectors picker in `chatwidget`.
With these changes, only the apps/connectors picker uses this new
option, though it could be used elsewhere in the future.

Why: previously, the description column was computed from only currently
visible rows, so as you scrolled or filtered, the column could shift and
cause wrapping/height changes that looked jumpy. Computing it from all
rows in this popup keeps alignment and layout consistent as users scroll
through avaialble apps.



**Before:**

https://github.com/user-attachments/assets/3856cb72-5465-4b90-a993-65a2ffb09113





**After:**

https://github.com/user-attachments/assets/37b9d626-0b21-4c0f-8bb8-244c9ef971ff

codex-rs/tui/src/bottom_pane/mod.rs

@@ -65,6 +65,7 @@ mod skill_popup;
 mod skills_toggle_view;
 mod slash_commands;
 pub(crate) use footer::CollaborationModeIndicator;
+pub(crate) use list_selection_view::ColumnWidthMode;
 pub(crate) use list_selection_view::SelectionViewParams;
 mod feedback_view;
 pub(crate) use feedback_view::FeedbackAudience;