Add tests, fix offset logic, and bump dependencies

- Introduce a comprehensive test suite (cli, app, board, tasks, audio)
  and a
  new TESTING.md document describing test execution.
- Correct vertical offset calculation in `BoardState` to use saturating
  subtraction and ceiling division.
- Clamp initial `Offset` values to the provided maximum in
  `Offset::new`.
- Export `load_audio` from the audio thread module and switch to
  `LoopedDecoder` for proper OGG looping.
- Update several crate versions: clap, ratatui, log, rodio, and
  bitflags.

src/app/states/skirmish_states/board.rs

@@ -51,7 +51,7 @@ impl BoardState {
         let h_max_offset: usize = Self::max_offset(map_width, cols);
 
         let vertical_offset: Offset = Offset::new(
-            Some((map_height - rows as usize + 1) / 2),
+            Some(map_height.saturating_sub(rows).div_ceil(2)),
             Some(v_max_offset),
         );
         let horizontal_offset: Offset = Offset::new(None, Some(h_max_offset));

src/app/states/skirmish_states/offset.rs

@@ -7,7 +7,7 @@ pub struct Offset {
 impl Offset {
     pub fn new(initial_value: Option<usize>, initial_max: Option<usize>) -> Self {
         Self {
-            value: initial_value.unwrap_or(0),
+            value: initial_value.unwrap_or(0).min(initial_max.unwrap_or(0)),
             max: initial_max.unwrap_or(0),
         }
     }
@@ -17,11 +17,12 @@ impl Offset {
     }
 
     pub fn set_value(&mut self, value: usize) {
-        self.value = value;
+        self.value = value.min(self.max);
     }
 
     pub fn set_max(&mut self, max: usize) {
         self.max = max;
+        self.value = self.value.min(max);
     }
 
     pub fn next(&mut self) {

src/app/states/skirmish_states/tasks/digging.rs

@@ -1,5 +1,5 @@
 use crate::app::states::skirmish_states::tasks::Task;
-use std::{collections::VecDeque, ops::Add};
+use std::collections::VecDeque;
 
 #[derive(Debug, Clone, PartialEq)]
 pub struct DiggingTask {
@@ -49,7 +49,7 @@ impl Task for DiggingTask {
     }
 
     fn progress(&mut self) {
-        let _ = self.progress.add(self.tick_increase).max(0.0).min(100.0);
+        self.progress = (self.progress + self.tick_increase).clamp(0.0, 100.0);
     }
 
     fn is_finished(&self) -> bool {