Some tweaks to (hopefully) make some loops a little faster to grok

A little use of the newer optional chaning operator to make some repetetive conditionals slightly faster to read.

Some targeted use of `.some()` and `.includes()` to convey the intention in compact fashion.

Some rewrites involving `Set`s, often involved in making it easier to grok what’s populating the set at a glance.

The standard functional tools for manipulating Arrays (usually `.map()` and `.filter()`) make it easy to write some code that reads a little bit like a pipeline.

Some small rewrites can make these even easier to read. If the arrow function is short enough, using the single-line syntax can make it less  noisy by avoiding the need for braces `{`|`}` or `return`.

Using the static methods _directly_ for the callback is even better, since it’s not even necessary to use an anonymous arrow function or name any arguments.

As I have recently learned, `Object.values()` already returns an Array. :D

(Rather than decide between using `target` or `path` in the loop body, I just smooshed them together.)