Refactor skirmish tasks and update dependencies

- Disable automatic board.advance_turn and replace it with explicit unit
  movement handling.
- Add Tunnel structure creation during digging tasks.
- Extend DiggingTask with pop_front and current_target helpers.
- Rename task getters to get_ref_tasks and add mutable get_mut_tasks.
- Update Unit trait and Units enum to expose these new methods.
- Remove unused EMPTY_TASKS lazy static.
- Bump flake.lock revisions, hashes, and timestamps for several
  dependencies.

src/app/states/skirmish_states/units/miner.rs

@@ -79,10 +79,14 @@ impl Unit for MinerUnit {
         self.coords
     }
 
-    fn get_tasks(&self) -> &VecDeque<Tasks> {
+    fn get_ref_tasks(&self) -> &VecDeque<Tasks> {
         &self.tasks
     }
 
+    fn get_mut_tasks(&mut self) -> &mut VecDeque<Tasks> {
+        &mut self.tasks
+    }
+
     fn get_tasks_formatted(&self) -> Vec<Line<'_>> {
         Vec::from(
             self.tasks

src/app/states/skirmish_states/units/unit_trait.rs

@@ -26,7 +26,9 @@ pub trait Unit {
 
     fn get_coords(&self) -> (usize, usize);
 
-    fn get_tasks(&self) -> &VecDeque<Tasks>;
+    fn get_ref_tasks(&self) -> &VecDeque<Tasks>;
+
+    fn get_mut_tasks(&mut self) -> &mut VecDeque<Tasks>;
 
     fn set_task(&mut self, task: Tasks);
 
@@ -39,7 +41,7 @@ pub trait Unit {
         let hp_percent: u16 = hp * 100 / max_hp;
         let can_dig: bool = self.get_can_dig();
         let digging_power: f32 = self.get_digging_power();
-        let have_any_tasks: bool = self.get_tasks().is_empty();
+        let have_any_tasks: bool = self.get_ref_tasks().is_empty();
         let tasks: Vec<Line<'_>> = self.get_tasks_formatted();
 
         let mut lines: Vec<Line<'_>> = Vec::from([

src/app/states/skirmish_states/units/units_enum.rs

@@ -3,12 +3,9 @@ use crate::app::states::skirmish_states::{
     tasks::Tasks,
     units::{MinerUnit, Unit},
 };
-use once_cell::sync::Lazy;
 use ratatui::text::Line;
 use std::collections::VecDeque;
 
-static EMPTY_TASKS: Lazy<VecDeque<Tasks>> = Lazy::new(|| VecDeque::new());
-
 #[derive(Debug, Clone, PartialEq)]
 pub enum Units {
     Miner(MinerUnit),
@@ -16,14 +13,14 @@ pub enum Units {
 
 impl Units {
     #[inline]
-    fn u(&self) -> &dyn Unit {
+    pub fn u(&self) -> &dyn Unit {
         match self {
             Self::Miner(m) => m,
         }
     }
 
     #[inline]
-    fn u_mut(&mut self) -> &mut dyn Unit {
+    pub fn u_mut(&mut self) -> &mut dyn Unit {
         match self {
             Self::Miner(m) => m,
         }
@@ -63,8 +60,12 @@ impl Unit for Units {
         self.u().get_coords()
     }
 
-    fn get_tasks(&self) -> &VecDeque<Tasks> {
-        self.u().get_tasks()
+    fn get_ref_tasks(&self) -> &VecDeque<Tasks> {
+        self.u().get_ref_tasks()
+    }
+
+    fn get_mut_tasks(&mut self) -> &mut VecDeque<Tasks> {
+        self.u_mut().get_mut_tasks()
     }
 
     fn get_tasks_formatted(&self) -> Vec<Line<'_>> {
@@ -113,8 +114,16 @@ impl Unit for Option<Units> {
         self.as_ref().map_or((0, 0), |u| u.get_coords())
     }
 
-    fn get_tasks(&self) -> &VecDeque<Tasks> {
-        self.as_ref().map_or(&EMPTY_TASKS, |u| u.get_tasks())
+    fn get_ref_tasks(&self) -> &VecDeque<Tasks> {
+        self.as_ref()
+            .expect("attempted to get referenced tasks from `None`")
+            .get_ref_tasks()
+    }
+
+    fn get_mut_tasks(&mut self) -> &mut VecDeque<Tasks> {
+        self.as_mut()
+            .expect("attempted to get mutable tasks from `None`")
+            .get_mut_tasks()
     }
 
     fn get_tasks_formatted(&self) -> Vec<Line<'_>> {