Add cleanup system to destroy dead entities

Author: HTRMC

src/ecs/ecs.zig

@@ -83,6 +83,9 @@ pub fn initSystems(world: *World) !void {
     try world.addSystem("physics", systems.physics_system.run, .update, 50);
     try world.addSystem("animation", systems.animation_system.run, .update, 60);
 
+    // Post-update phase - cleanup dead entities
+    try world.addSystem("cleanup", systems.cleanup_system.run, .post_update, 0);
+
     // Render prep phase
     try world.addSystem("render_prep", systems.render_prep_system.run, .render_prep, 0);
 }

src/ecs/systems/cleanup_system.zig

@@ -0,0 +1,26 @@
+const World = @import("../world.zig").World;
+const Tags = @import("../components/tags.zig").Tags;
+const EntityId = @import("../entity.zig").EntityId;
+
+/// Cleanup system - destroys entities marked for removal
+/// Runs in post_update phase after all game logic has finished
+pub fn run(world: *World) void {
+    // Collect entities to destroy (avoid mutating during iteration)
+    var to_destroy: [256]EntityId = undefined;
+    var count: usize = 0;
+
+    var entity_iter = world.entities.iterator();
+    while (entity_iter.next()) |id| {
+        const tags = world.getComponent(Tags, id) orelse continue;
+        if (tags.marked_for_removal) {
+            if (count < to_destroy.len) {
+                to_destroy[count] = id;
+                count += 1;
+            }
+        }
+    }
+
+    for (to_destroy[0..count]) |id| {
+        world.destroyEntity(id);
+    }
+}

src/ecs/systems/systems.zig

@@ -10,3 +10,4 @@ pub const physics_system = @import("physics_system.zig");
 pub const render_prep_system = @import("render_prep_system.zig");
 pub const player_input_system = @import("player_input_system.zig");
 pub const player_movement_system = @import("player_movement_system.zig");
+pub const cleanup_system = @import("cleanup_system.zig");