Extend content loader to read and instantiate real YAML content into
ECS entities. 2-phase spawn pipeline: Phase 1 creates entities with
core components (Want, Tolerance, Contentment, Personality, Tells,
Skills), Phase 2 resolves cross-references (Relationships, Secrets,
Information via KnowledgeGraph, DailyRoutine).
Loads enums, entity attributes, pools, templates, triangles, and NPC
profiles. Handles stub files gracefully. 7 integration tests against
real content files plus edge case tests for invalid data.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>