Add replay system

src/args.rs

@@ -1,5 +1,6 @@
 use bevy::prelude::*;
 use clap::Parser;
+use std::path::PathBuf;
 
 #[derive(Parser, Debug, Clone, Resource)]
 #[command(version, about, long_about = None)]
@@ -12,4 +13,13 @@ pub struct Args {
     pub check_distance: usize,
     #[clap(long, default_value_t = 1)]
     pub players: usize,
+    /// Record a replay to this path.
+    #[clap(long, conflicts_with = "play_replay")]
+    pub record_replay: Option<PathBuf>,
+    /// Play a replay from this path.
+    #[clap(long, conflicts_with = "record_replay")]
+    pub play_replay: Option<PathBuf>,
+    /// Replay output format. JSON is useful for inspection; binary is compact.
+    #[clap(long, value_enum, default_value_t = crate::replay::ReplayFormat::Binary)]
+    pub replay_format: crate::replay::ReplayFormat,
 }