chore: improve clsx maintenance path

[quyentonndbs]

Summary:

• Add edge-case unit tests in test/lite.js for the lite build covering inputs the lite variant explicitly does not support (objects, nested arrays) to lock in documented behavior and guard against regressions; assertions follow the existing uvu/assert patterns already used in the test file.
• Keep the change narrow so it is straightforward to review.

Notes:

• I kept this scoped to the relevant implementation and tests.