Add side panel and refactor title helpers

Introduce a `side_panel` flag throughout the skirmish state, board
creation,
and cell area calculation to enable a detachable side panel. Refactor
the
title helper to own its strings and use a static separator, updating the
single‑title helper accordingly. Add a new `SidePanelWidget` and expose
the
`skirmish_main_area_layout` helper. Extend keybindings with `Tab` and
`ShiftTab` actions under a new `Opener` group. Update structures and
units
to implement a `get_name` method and adjust related traits and imports.

src/app/keybindings/skirmish.rs

@@ -3,12 +3,14 @@ use crate::app::{
     keybindings::{Action, common_keybindings, event_to_action},
     states::skirmish_states::{BoardState, MoveFocusedCell, ZoomLevel},
 };
-use ratatui::crossterm::event::KeyEvent;
+use ratatui::{crossterm::event::KeyEvent, layout::Rect};
 
 pub fn skirmish_keybindings(app: &mut App, key_event: &KeyEvent) {
     if let Some(action) = event_to_action(&key_event) {
         common_keybindings(app, action);
 
+        let window_area: Rect = app.window_area;
+
         let Some(states) = app.states_mut() else {
             return;
         };
@@ -86,6 +88,10 @@ pub fn skirmish_keybindings(app: &mut App, key_event: &KeyEvent) {
                 board.marking_cells = false;
                 board.clear_marked_cells()
             }
+            Action::Tab => {
+                states.skirmish.side_panel = !states.skirmish.side_panel;
+                board.change_resize(&window_area, states.skirmish.side_panel);
+            }
             _ => (),
         }
     }