Add rustfmt configuration and reformat code

- Document new Rust formatting standards in AGENTS, CODE_MAP, and
  PROGRESS.
- Add rustfmt.toml with style 2024, 2‑space indents, 100‑char width, LF
  endings.
- Apply consistent 2‑space indentation and ordering across source files.
- Minor clean‑up of imports and whitespace to match the new style.

src/app/helpers/cells_area.rs

@@ -1,17 +1,17 @@
 use crate::app::views::{skirmish_layout, skirmish_main_area_layout};
 use ratatui::{
-    layout::{Margin, Rect},
-    widgets::{Block, Borders},
+  layout::{Margin, Rect},
+  widgets::{Block, Borders},
 };
 
 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];
+  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(board_area)
-        .inner(Margin {
-            horizontal: 1,
-            vertical: 1,
-        })
+  Block::new()
+    .borders(Borders::LEFT | Borders::TOP | Borders::RIGHT)
+    .inner(board_area)
+    .inner(Margin {
+      horizontal: 1,
+      vertical: 1,
+    })
 }