test: standardize test imports across test suite

- Add consistent Bun test framework imports to all test files
- Remove duplicate import statements
- Ensure uniform import style for describe, expect, and test functions
- Simplify test file import configurations

__tests__/helpers.test.ts

@@ -1,4 +1,5 @@
 import { describe, expect, test } from "bun:test";
+import { describe, expect, test } from "bun:test";
 import { formatToolCall } from "../src/utils/helpers";
 
 describe('helpers', () => {