refactor: use package imports over relative imports for cross package ref and tests

packages/core/src/index.ts

@@ -1,4 +1,5 @@
 export * from "./attribute.js";
 export * from "./entity.js";
 export * from "./world.js";
+export * from "./clock.js";
 export * from "./repository.js";

packages/core/tests/core.test.ts

@@ -4,11 +4,11 @@ import {
   Attribute,
   AttributeVisibility,
   AttributableObject,
-} from "../src/attribute.js";
-import { Entity } from "../src/entity.js";
-import { WorldClock } from "../src/clock.js";
-import { WorldState } from "../src/world.js";
-import { SQLiteRepository } from "../src/repository.js";
+  Entity,
+  WorldClock,
+  WorldState,
+  SQLiteRepository,
+} from "@omnia/core";
 
 // A concrete implementation of AttributableObject for testing
 class MockAttributable extends AttributableObject {}