Add frontend callback

[vxgmichel]

Also partially address #37 (only for the servers)
Configuration handling and keyboard detection has also been refactored for the servers.

[vxgmichel]

Hi @jquast 👋
Now that this PR is merged, I deployed a tiny frontend on telnet gambaterm.vxgmichel.com 23023 🎉
It's 150 lines of vibe-coded blessed app, but I can give you access to the demo repository if you're interesed.

[jquast]

Looks great!

I'll probably pick up the sixel/kitty branch again soon, just needed testing and refining. I worked on kitty+sixel support for another project with good success, I was able to make a pure python sixel+kitty encoders using only numpy and plain python at very high refresh rate without libsixel.

There is another like yours recently released by the way, but as a "Synchronet/BBS Door", which means the install and player experience is a real PITA -- the sysop must install synchronet or mystic bbs, and the user must use a special client (SyncTERM) and sign in and register for an account and navigate a bbs to find the door to play it. It does use a SyncTerm-propriatary audio via DEC "APC" command interface, so that's interesting, but not implemented on any other terminal i know of.

And, its CP437 encoding only (yuck!). https://github.com/hmderdoc/lameboy/ -- syncterm doesn't support utf-8

I haven't tried it, I don't think I will because I already know what it looks like, I made CP437 experiments earlier. I think your approach of supporting all modern terminals, and with minimal interface w/o 3rd party dependencies is best.