Refactor Units enum location and chain CellWidget setters

Move Units enum from the units module into the skirmish state module,
add a dedicated Players enum, and remove the now‑unused unit module.
Update all imports accordingly.
Adjust CellWidget's set_zoom_level and set_structure to return &mut
Self,
enabling method chaining.

src/app/states/mod.rs

@@ -9,5 +9,5 @@ pub use main_menu::MainMenuState;
 pub use perk_decks::{PerkDecks, PerkDecksState};
 pub use settings::SettingsState;
 pub use skills_config::SkillsConfigState;
-pub use skirmish::{CellStructure, GameMode, Players, SkirmishState, ZoomLevel};
+pub use skirmish::{CellStructure, GameMode, Players, SkirmishState, Units, ZoomLevel};
 pub use skirmish_states::{FocusedCell, Offset};

src/app/states/skirmish.rs

@@ -1,4 +1,4 @@
-use crate::app::{buildings::BaseBuilding, states::skirmish_states::BoardState};
+use crate::app::{buildings::BaseBuilding, states::skirmish_states::BoardState, units::MinerUnit};
 use clap::ValueEnum;
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -21,6 +21,12 @@ pub enum ZoomLevel {
     ZoomedOut,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Players {
+    Player,
+    Enemy,
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum CellStructure {
     Base(BaseBuilding),
@@ -29,7 +35,6 @@ pub enum CellStructure {
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum Players {
-    Player,
-    Enemy,
+pub enum Units {
+    Miner(MinerUnit),
 }

src/app/states/skirmish_states/board.rs

@@ -2,9 +2,10 @@ use crate::app::{
     buildings::BaseBuilding,
     helpers::{CellSizes, cell_size_helper, cells_area_helper},
     states::{
-        CellStructure, FocusedCell, Offset, Players, ZoomLevel, skirmish_states::MoveFocusedCell,
+        CellStructure, FocusedCell, Offset, Players, Units, ZoomLevel,
+        skirmish_states::MoveFocusedCell,
     },
-    units::{MinerUnit, Units},
+    units::MinerUnit,
     widgets::CellWidget,
 };
 use ratatui::layout::Rect;

src/app/units/mod.rs

@@ -1,5 +1,3 @@
 pub mod miner;
-pub mod unit;
 
 pub use miner::MinerUnit;
-pub use unit::Units;

src/app/units/unit.rs

@@ -1,6 +0,0 @@
-use crate::app::units::MinerUnit;
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum Units {
-    Miner(MinerUnit),
-}

src/app/widgets/cell.rs

@@ -1,7 +1,4 @@
-use crate::app::{
-    states::{CellStructure, Players, ZoomLevel},
-    units::Units,
-};
+use crate::app::states::{CellStructure, Players, Units, ZoomLevel};
 use ratatui::{
     buffer::Buffer,
     layout::{Alignment, Rect},
@@ -46,12 +43,14 @@ impl CellWidget {
         self
     }
 
-    pub fn set_zoom_level(&mut self, zoom_level: ZoomLevel) {
+    pub fn set_zoom_level(&mut self, zoom_level: ZoomLevel) -> &mut Self {
         self.zoom_level = zoom_level;
+        self
     }
 
-    pub fn set_structure(&mut self, sctructure: CellStructure) {
+    pub fn set_structure(&mut self, sctructure: CellStructure) -> &mut Self {
         self.structure = sctructure;
+        self
     }
 
     pub fn get_marked(&self) -> bool {