Added a basic MemoryArena.

Added one scratch, one engine and one game arena.
Converted the game alloc to arena + the display stuff.
WIP

Made using Antigravity+gemini

.agent/rules/coding-guidelines.md

@@ -0,0 +1,10 @@
+---
+trigger: always_on
+---
+
+No exceptions
+Use [[nodiscard]]
+auto is allowed but when its a pointer add the * and when reference adds the &
+Member variable are CamelCase
+Types are CamelCase
+Functions are CamelCase.