test: migrate test suite from Jest to Bun test framework

- Convert test files to use Bun's test framework and mocking utilities
- Update import statements and test syntax
- Add comprehensive test utilities and mock implementations
- Create test migration guide documentation
- Implement helper functions for consistent test setup and teardown
- Add type definitions for improved type safety in tests

src/utils/helpers.ts

@@ -0,0 +1,12 @@
+/**
+ * Formats a tool call response into a standardized structure
+ * @param obj The object to format
+ * @param isError Whether this is an error response
+ * @returns Formatted response object
+ */
+export const formatToolCall = (obj: any, isError: boolean = false) => {
+    const text = obj === undefined ? 'undefined' : JSON.stringify(obj, null, 2);
+    return {
+        content: [{ type: "text", text, isError }],
+    };
+};