Add Vim buffer jump motions (#40958)

## What changed

- Add `gg` and `G` motions to jump to the first and last buffer lines.
- Support the motions with delete, change, and yank operators, including dot-repeat for edits.
- Expose normal-mode and operator-motion bindings in the configurable keymap while preserving conflicting user bindings.

## Testing

- Cover buffer jumps, operator combinations, repeat behavior, chord routing, and custom remapping.

GitOrigin-RevId: 24a9178cf7964053aaf9a8cd268c5434dda0778e

codex-rs/config/src/tui_keymap.rs

@@ -243,6 +243,10 @@ pub struct TuiVimNormalKeymap {
     pub till_forward: Option<KeybindingsSpec>,
     /// Stop after the previous character on the current line (`T`).
     pub till_backward: Option<KeybindingsSpec>,
+    /// Begin a jump to the first buffer line (`gg`).
+    pub jump_top: Option<KeybindingsSpec>,
+    /// Jump to the last buffer line (`G`).
+    pub jump_bottom: Option<KeybindingsSpec>,
     /// Delete character under cursor (`x`).
     pub delete_char: Option<KeybindingsSpec>,
     /// Replace the character under the cursor (`r`).
@@ -308,6 +312,10 @@ pub struct TuiVimOperatorKeymap {
     pub motion_till_forward: Option<KeybindingsSpec>,
     /// Motion: stop after the previous character on the current line (`T`).
     pub motion_till_backward: Option<KeybindingsSpec>,
+    /// Motion: begin a jump to the first buffer line (`gg`).
+    pub motion_jump_top: Option<KeybindingsSpec>,
+    /// Motion: jump to the last buffer line (`G`).
+    pub motion_jump_bottom: Option<KeybindingsSpec>,
     /// Select an inner text object after an operator.
     pub select_inner_text_object: Option<KeybindingsSpec>,
     /// Select an around text object after an operator.