Set methods in ES2025, and the lodash import I removed

Union, intersection and difference on Set, in the language, replacing four utility functions and a dependency.

const enabled = new Set(featureFlags)
const required = new Set(['billing', 'exports'])

required.difference(enabled)       // missing
enabled.intersection(required)     // present
enabled.isSupersetOf(required)     // a boolean

// and the array round trip these replace:
//   [...new Set([...a].filter(x => b.has(x)))]

The array round trip was the idiom and it allocated twice for a question that needs no allocation at all. Removing the dependency was not the point — it was one import out of a package we still use for two other things — and the readability difference on a set operation expressed as a filter over a spread is substantial.