Remove lodash.merge dependency

Editor assessment

The subject states the change: the lodash.merge dependency was removed. The body then supplies exactly what a reviewer wants: lodash.mergeWith replaces it, and the two behave identically when the last argument is not a function — a precise compatibility condition that tells readers the swap is safe and under what caveat. That is a real trade-off explanation in one sentence. The refactor type matches, the imperative subject is clean, no scope is needed for a utility swap, and no footers are required. An exemplary small commit.