Add explanation of STATIC_ASSERTS in pokemon.c

[pkmnsnfrn]

Original discussion: https://discord.com/channels/419213663107416084/774393519569502268/1220032007225217046

I don't feel strongly about how this is worded, but I think an explanation is a good idea. If this turns out to be a common / bigger issue, we can circle back.

[mrgriffin]

I think it would be worth adding a brief note that unless there's unused data after your member, naively growing the member will likely break the save... and perhaps that a third alternative would be to repurpose some IDs that have never been used by your game?

I could imagine established projects choosing that third path. (There's also a fourth path of using a non-contiguous bit, and then combining them in GetMonData/separating them in SetMonData, but that's probably too wordy and fiddly to explain)

[pkmnsnfrn]

@mrgriffin could you clarify IDs that you think developers wouldn't use? I just want to make sure I understand it before giving an example (and yeah, I'm skipping path 4 lmao, if you're skilled enough to do that, you're not reading my comment at all)

[mrgriffin]

Probably the most common examples will be key items—e.g. Gold Teeth or Magma Emblem. But also potentially things like a developer going "well I never want Tera Shards", or "I don't have Giratina" and so not having Griseous Orb and/or Core.

Similarly, if they've decided to permanently turn off species then they might decide to repurpose those IDs.

[mrgriffin]

tysm!