feat(creatures): add creature types, data, ECS components, and core systems
Phase 5.1-5.5: Creatures & Ecology foundation
- 3 species data (Crystallid, Acidophile, Reagent) with real chemistry
- ECS components: Creature, AI, Metabolism, LifeCycle
- AI FSM system: idle → wander → feed → flee → attack
- Metabolism: energy drain, feeding from resources, starvation damage
- Life cycle: egg → youth → mature → aging → natural death
- Population dynamics: counting, reproduction, initial spawning
- Species registry with numeric/string ID lookup
- 51 tests passing (272 total)
Co-authored-by: Cursor <cursoragent@cursor.com>
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