Add documentation

Extensive doc comments were added to keybindings, CLI options, logging,
and
widget modules. The `count_largest_group` function was introduced to
compute
the largest group size among actions. CLI validation for
`skill_points_limit`
was broadened to a 90‑690 range. Imports and signatures for `Display`
were
adjusted accordingly.

src/app/states/perk_decks.rs

@@ -1,5 +1,5 @@
 use clap::ValueEnum;
-use std::fmt::Display;
+use std::fmt::{Display, Formatter, Result};
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct PerkDecksState {
@@ -16,7 +16,7 @@ pub enum PerkDecks {
 }
 
 impl Display for PerkDecks {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
         match self {
             PerkDecks::Silesian => write!(f, "Silesian"),
             PerkDecks::BogeyMan => write!(f, "Bogey Man"),