Update the Chat page to highlight Discord info and de-emphasize/remove outdated links

The gbdev.io home page has, at the very top:

> **Game Boy Development community**
>
> We are a non for profit collective of passionate developers and hackers working on development tools, homebrew games, emulators, preservation and documentation for the Nintendo Game Boy handheld console, the original gray brick from 1989.
>
> Join us on [GitHub](https://github.com/gbdev), [Mastodon](https://fedi.gbdev.io/@gbdev), [BlueSky](https://bsky.app/profile/gbdev.io), [Twitter](https://twitter.com/gbdev0) and [Discord](https://gbdev.io/chat.html).

This is great! All the social links are actively updated, and the Discord link is where the reader can truly *join* the community, and start chatting with us. (Maybe it should be listed first?)

However, the [Chat](https://gbdev.io/chat.html) page is not. Here's what it currently says:

> [**Community channels**](https://gbdev.io/chat.html#community-channels)
>
> Join our community on the following channels. Before posting, read the rules and the FAQ (usually in the welcome threads or in the signup).
>
> - [Discord Server](https://discord.gg/RjJKA8wrD4).
> - IRC: [`#gbdev` on Libera.chat](https://web.libera.chat/#gbdev) is bridged to the Discord chat.
> - `#gbdev-ot`, `#gbdev-casual`, `#gbdev-hw`, `#gbdev-meta`, `#gbdev-asm`, `#gbdev-gfx`, `#gbdev-emudev`, `#gbdev-romhacking` and `#gbdev-research` are also available for discussion about specific topics.
> - Forum: https://gbdev.gg8.se/forums/
> - Wiki: https://gbdev.gg8.se/wiki/

The first link is fine, but I think the second link looks a lot more important than it is (to the point of de-emphasizing the first link where we actually want people to go), and the last two links are basically dead.

The GBDev Discord is *the* place where members new and old can actually communicate. I think the "Before posting, read the rules and the FAQ" instruction should be a sub-bullet of this link, so it can be more precise about where to find that info once you join the server.

The IRC server basically just exists in 2026 as a bridge to Discord, and even that only for perhaps a dozen[^1] people. (Only one of whom I'd recognize as actually regularly using it, beware.) We shouldn't encourage new users to do the same, since it can't handle replies, videos, reactions, etc. But having the longest list item makes it look more important than it is.

The forum looks dead. The last post in its "Site News" is from 2019. Only 2 of the 7 sub-forums have posts from 2026, and only the one from March has a reply (the one from February went unanswered). (It's now July.)

The wiki also looks dead. I mostly know it as being the old Pan Docs site -- the very first link in the very first section of its Main Page, "Developer Information -> Documentation", starts off with a big red "The copy of Pan Docs hosted on this wiki is considered deprecated" banner (as some may recognize from outdated links via Google et al). I thought maybe there'd be more than just the old Pan Docs, since supposedly "A few articles up -> There a couple of articles up on the Wiki." But as of today there were [no changes to any page in the last 30 days](https://gbdev.gg8.se/wiki/index.php?title=Special:RecentChanges&hidebots=0&days=30). (It's not even really a "chat" method; still at least a collaborative community effort, but nobody new to the community should be futilely trying to share info by editing this website.)

I don't think these should all still be presented as four equal-weight options. Explaining how to join and use the Discord server should be the primary purpose of this page. Then maybe in a `

---

`-separated bottom section, or some other clearly secondary area, it could list the IRC, wiki, and forums as historical alternatives, and mention that they're less likely to be read/responded to any more.

[^1]: **Edit:** Turns out that, not counting me, there's 13, a whole baker's dozen! None of whom are talking. :P Oh, and one is the `gb-bridge` bot, so I guess it's max 12 real humans after all. Even the `#pret` channel has 25 others, despite pret only mentioning it at pret.github.io, not in its repos' READMEs.

Locate the source file that renders chat.html and review the Community channels section. Make Discord the primary option with its rules and FAQ guidance, and clearly mark IRC, the forum, and wiki as secondary or outdated alternatives; verify the rendered Chat page and its links.

Rédigé par le modèle d'indexation à partir du texte de l'issue.