Refactor skirmish focus handling and CellWidget API

Introduce a MoveFocusedCell enum and a BoardState.change_focused_cell
method to
centralize focus movement logic. Update skirmish keybindings to use this
new
method and simplify board rendering by directly using stored CellWidget
state.
Make CellWidget setters chainable and expose the new enum in the module
re‑exports. Remove duplicated max_offset logic and old move_* methods.

src/app/states/skirmish_states/focused_cell.rs

@@ -1,3 +1,10 @@
+pub enum MoveFocusedCell {
+    Up,
+    Down,
+    Left,
+    Right,
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct FocusedCell {
     row: usize,
@@ -24,19 +31,22 @@ impl FocusedCell {
         self.col
     }
 
-    pub fn move_up(&mut self) {
-        self.row = self.row.saturating_sub(1).max(0);
-    }
+    pub fn move_focused_cell(&mut self, direction: MoveFocusedCell) -> (usize, usize) {
+        match direction {
+            MoveFocusedCell::Up => {
+                self.row = self.row.saturating_sub(1).max(0);
+            }
+            MoveFocusedCell::Down => {
+                self.row = self.row.saturating_add(1).min(self.max_row - 1);
+            }
+            MoveFocusedCell::Left => {
+                self.col = self.col.saturating_sub(1).max(0);
+            }
+            MoveFocusedCell::Right => {
+                self.col = self.col.saturating_add(1).min(self.max_col - 1);
+            }
+        }
 
-    pub fn move_down(&mut self) {
-        self.row = self.row.saturating_add(1).min(self.max_row - 1);
-    }
-
-    pub fn move_left(&mut self) {
-        self.col = self.col.saturating_sub(1).max(0);
-    }
-
-    pub fn move_right(&mut self) {
-        self.col = self.col.saturating_add(1).min(self.max_col - 1);
+        (self.row, self.col)
     }
 }