Rework input buffer to match HDR closer (#79)

## Summary

- Preserve distinct same-action bindings in rollback input frames.
- Add independent command lifetimes with tap and state-scoped hold buffering.
- Detect second shield bindings and consume shield commands for air dodge.
- Fix duplicate keyboard mappings being overwritten.

Reviewed-on: #79
Co-authored-by: Álex Román Núñez <eirexe@eirteam.moe>

src/input/map.rs

@@ -19,6 +19,17 @@ pub enum InputMapAction {
     Attack,
 }
 
+impl InputMapAction {
+    pub const fn digital_action(&self) -> Option<crate::input::DigitalAction> {
+        match self {
+            Self::Jump => Some(crate::input::DigitalAction::Jump),
+            Self::Shield => Some(crate::input::DigitalAction::Shield),
+            Self::Attack => Some(crate::input::DigitalAction::Attack),
+            Self::MovementXDir(_) | Self::MovementYDir(_) => None,
+        }
+    }
+}
+
 #[derive(Debug)]
 pub enum MenuInputMapAction {
     MovementXDir(i32),
@@ -32,6 +43,7 @@ pub enum MenuInputMapAction {
 pub struct KeyboardInputMapElement {
     pub key: KeyCode,
     pub action: InputMapAction,
+    pub binding_slot: u8,
 }
 
 #[derive(Debug)]
@@ -44,6 +56,7 @@ pub enum GamepadBinding {
 pub struct GamepadInputMapElement {
     pub binding: GamepadBinding,
     pub action: InputMapAction,
+    pub binding_slot: u8,
 }
 
 #[derive(Debug)]