Osrs env upstream

[valtterivalo]

two (currently) OSRS environments (or encounters as i call them inside this broader OSRS env) in pure C. the env itself and its backend has a ton of OSRS logic already that supports building new encounters pretty easily, but abstractions for this could be way better. we'll see where that goes naturally after we start implementing more encounters. ofc i'd rather have the entire damn playable game as a single functional environment but let's be honest about the amount of work involved.

osrs_pvp: NH PvP with 24 scripted opponents (trivial to onetick+action-reading), PFSP support, 7-head discrete action space (39 logits), 373-dim obs. full combat: gear switching, prayers, eating, specs, movement, action masking.

osrs_zulrah: money snek solo boss encounter, trying to be as faithful as possible to the real deal but some work remains with more ambiguous mechanics. 3 gear tiers with all special effects etc covered (tbow scaling, sang heal, crystal set bonus, eye of ayak magic drain, confliction double-roll, thralls). basic reward shaping for training, i couldn't get budget setup to win without shaping. bis gear obviously shits on the snake with no problems.

binary data assets (sprites, models, collision maps) gitignored, regenerated from OSRS cache via included python scripts that are pretty easy to read and understand. expect there to be quite a bit of coordinate system flipping and offset trial and error when implementing new areas and encounters, but that's part of the deal until we figure out something rigorous for that.