fix: onRefresh signature in lib test-utils omits required currentTokens parameter

[panz3r]

Context

Discovered during development of the showcase example (PR #252).

Problem

The MockAuthClient in lib/test/test-utils.tsx declares onRefresh as:

onRefresh(_minValidity?: number) { ... }

But the actual AuthClient interface requires currentTokens as the first parameter:

onRefresh(currentTokens: T, minValidity?: number): Promise<T>

This means the mock implementation silently omits the required first argument, which misleads anyone reading the test utilities to learn the API contract for onRefresh.

Impact

• New contributors studying the tests to understand the AuthClient interface will learn the wrong signature for onRefresh.
• Any test relying on currentTokens passed to onRefresh would silently receive undefined instead.

Proposed Action

Update onRefresh in lib/test/test-utils.tsx to match the correct interface signature, including the currentTokens parameter.