refactor: transition to struct-of-arrays ECS architecture

- Replace individual Entity structs with centralized component slices in Game struct (SoA layout).
- Implement bitmask-based component lookup (CM_Position, CM_Move, etc.).
- Convert logic from object-oriented Update() methods to standalone Systems (UpdateMoveSystem, UpdateGatherSystem, UpdateSpawnSystem).
- Update rendering, selection, and input handling to iterate over component arrays.

2 files changed, 18 insertions, 7 deletions

diff --git a/ecs/component.go b/ecs/component.go
index 29ef967..ff22e53 100644
--- a/ecs/component.go
+++ b/ecs/component.go
@@ -1,10 +1,18 @@
 package ecs
 
-type Component[T any] struct {
-	IsEnabled bool
-	Value     T
-}
+type Mask uint16
 
-func C[T any](t T) Component[T] {
-	return Component[T]{IsEnabled: true, Value: t}
-}
+const (
+	CM_Position Mask = 1 << iota
+	CM_RelBounds
+	CM_Image
+	CM_Selection
+	CM_Move
+	CM_Order
+	CM_PatrolOrder
+	CM_GatherOrder
+	CM_ResourceGatherer
+	CM_ResourceSource
+	CM_ResourceStorage
+	CM_Spawn
+)
diff --git a/ecs/entity.go b/ecs/entity.go
new file mode 100644
index 0000000..636470c
--- /dev/null
+++ b/ecs/entity.go
@@ -0,0 +1,3 @@
+package ecs
+
+type Entity int