fix(tests): populate Set in idGenerator tests (#266)

[williamfds]

What

Add calls to ids.add(id) inside the loop in both idGenerator tests so that the Set is actually populated and the test detects real collisions.

Why

Without this line, the Set remains empty and ids.has(id) never returns true, making the test pass even if the generator produces duplicate IDs. With this change, we ensure the test only passes if there are truly no collisions.

Closes #266

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Checklist

• Run npm run test and npm run benchmark
• Tests and/or benchmarks are included (already existed and were adjusted)
• Documentation is changed or added (no docs affected)
• Commit message and code follow the Developer’s Certificate of Origin and the Code of Conduct