[DO NOT MERGE] bug: StateProxy prevents modification of object array properties

[TheAfroOfDoom]

context

this PR is purely to document a bug I noticed and went pretty deep to try and fix, but had did not resolve at time of writing

the high-level error was surfacing as this:

this was fixed in #1127 by removing that code path, but the root-cause of it may still cause issues in the future? tbd

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StateProxy

StateProxy uses JS Proxy's to give us redo/undo operations on objects

from my understanding StateProxy.create(obj) basically returns obj with some extra methods on it

you can still modify obj's properties as you'd expect, for example:

const obj = {}
const proxy = StateProxy.create(obj)

proxy.x = 2
// obj.x === 2
// proxy.x === 2

the bug

if an object has a pre-existing array property, however, that property seems to silently fail to be modified?

const obj = { arr: [1] }
const proxy = StateProxy.create(obj)

proxy.arr = [2]
// proxy.arr is still `[1]` ???

proxy.arr[0] = 3
// `proxy.arr[0]` is still `1` ?????

i didn't test deeper if this was an issue specific to StateProxys (something custom to Spyglass) or JS's Proxy's generally, but am dropping investigation on this for now since #1127 fixes the original bug i was looking into anyway