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/helpers/cells_area.rs

@@ -1,13 +1,15 @@
-use crate::app::views::skirmish_layout;
+use crate::app::views::{skirmish_layout, skirmish_main_area_layout};
 use ratatui::{
     layout::{Margin, Rect},
     widgets::{Block, Borders},
 };
 
-pub fn cells_area_helper(area: &Rect) -> Rect {
+pub fn cells_area_helper(area: &Rect, side_panel: bool) -> Rect {
+    let board_area: Rect = skirmish_main_area_layout(skirmish_layout(*area)[1], side_panel)[0];
+
     Block::new()
         .borders(Borders::LEFT | Borders::TOP | Borders::RIGHT)
-        .inner(skirmish_layout(*area)[1])
+        .inner(board_area)
         .inner(Margin {
             horizontal: 1,
             vertical: 1,