feat(app): vi-style j/k/g/G navigation in the load picker (#24)

Add j (down), k (up), g (first) and G (last) to the load picker's
list sub-mode, alongside the existing arrow keys. Typeable keys keep
the picker drivable by autocast in the website's documentation casts,
which cannot emit arrow keys. Footer hint left unchanged.

src/app.rs

@@ -2488,20 +2488,34 @@ impl App {
                     self.note_system(crate::t!("modal.load_cancelled"));
                     Vec::new()
                 }
-                KeyCode::Up => {
+                // `k` mirrors Up; vi-style keys keep the picker drivable by
+                // autocast, which can only emit typeable characters (#24).
+                KeyCode::Up | KeyCode::Char('k') => {
                     if state.selected > 0 {
                         state.selected -= 1;
                     }
                     self.modal = Some(Modal::LoadPicker(state));
                     Vec::new()
                 }
-                KeyCode::Down => {
+                // `j` mirrors Down (see the Up arm above).
+                KeyCode::Down | KeyCode::Char('j') => {
                     if state.selected + 1 < state.entries.len() {
                         state.selected += 1;
                     }
                     self.modal = Some(Modal::LoadPicker(state));
                     Vec::new()
                 }
+                // `g` jumps to the first entry, `G` to the last (vi convention).
+                KeyCode::Char('g') => {
+                    state.selected = 0;
+                    self.modal = Some(Modal::LoadPicker(state));
+                    Vec::new()
+                }
+                KeyCode::Char('G') => {
+                    state.selected = state.entries.len().saturating_sub(1);
+                    self.modal = Some(Modal::LoadPicker(state));
+                    Vec::new()
+                }
                 KeyCode::Enter => {
                     if let Some(entry) = state.entries.get(state.selected).cloned() {
                         self.modal = None;