Complete M11 Creator Studio and M12 Trust & Safety for PC5

- Creator Studio: Visual behavior & property inspector, GLB model importer, binary persistence
- Trust & Safety: 18+ TOS confirmation (DOB removed), creator guidelines & briefing card on join, in-game reporting HUD
- Test Harness: Add --filter, --skip-backend, --skip-godot to run_checkpoint_tests.py

backend/app/routers/discovery.py

@@ -37,10 +37,12 @@ class DiscoveredWorld(BaseModel):
     description: str | None = None
     category: str | None = None
     tags: list[str] = []
+    content_guidelines: str | None = None
     play_count: int = 0
     created_at: datetime | None = None
     owner: WorldOwnerSummary
 
+
     model_config = {"from_attributes": True}