Optimize ECS with Proper Data Structures

[aram-devdocs]

Labels: enhancement, performance, architecture
Depends on: #1

Description:
Current ECS implementation uses O(n) lookups and isn't a real ECS.

Current Problems:

• Linear search through all sprites for lookups
• Not actually an Entity-Component-System
• No spatial partitioning for collision detection

Tasks:

• Replace sprite lookup with HashMap<SpriteId, Sprite>
• Implement proper component storage
• Add spatial hashing for collision detection
• Consider migrating to established ECS library (hecs, bevy_ecs)

[aram-devdocs]

Tracked as ALPHA-F10 (ECS Improvements) in the alpha roadmap. See #125.

[claude]

Closing as superseded by #116 (F01: Core Stabilization). ECS data structure optimization is covered by F01 subtasks including #193 (F01-09: Fix hierarchy cascade deletion), #198 (F01-12: Add tests for parallel system execution safety), and the broader ECS architecture improvements planned under the alpha phase structure.

Triage: #158