feat: add Mage Arena minigame

[HarleyGilpin]

What

Implements the Mage Arena minigame

• Kolodion boss fight - shapeshifts through human (907) → ogre (908) → troll (11301) → dark beast (11302) → demon (911), owner-scoped NPC in the shared open wilderness arena, magic-only combat enforced, form progress persists so leaving/logging out resumes the fight at the same form with full HP.
• God capes - pray at the chamber statues for a cape; only one sacred cape can be owned at a time, dropping destroys it with the god-specific message.
• God spells - Saradomin Strike / Claws of Guthix / Flames of Zamorak are blocked outside the arena until cast 100 times inside (persistent per-spell counters). Impact gfx heights corrected (Saradomin/Guthix 100, Zamorak ground level).
• Chamber guardian -directs new arrivals to the statues, hands out a free staff matching the held cape, then opens the staff shop.
• Battle mages - aggressive god-spell casters that spare players wearing their god's cape and players mid-Kolodion-fight. Guthix mage uses gnome animations.
• Gundai - bank/PIN/collection dialogue plus Bank and Collect options. Lundail rune shop dialogue.
• Sparkling pools - walk to the edge tile, jump onto the pond with anim 7269 and splash, teleport between bank and chamber. Gated until Kolodion is defeated.
• Levers - mage bank entrance/exit via the generic lever teleports; arena levers gated on completion. All levers now blocked while teleblocked unless a forinthry bracelet is worn.
• Engine-adjacent fixes - multi-target spells no longer splash owner-scoped npcs (protects per-player bosses from bystander barrages).

Testing

20 WorldTest cases in MageArenaTest: full form chain, fight resume, owner/magic-only restrictions, cast gate (blocked outside / unlock at 100 / works after), battle mage cape exemptions, statue/cape rules, guardian staff grant, pool gating, lever teleblock + bracelet, stale-save form fallback. Full :game:test suite green.

[skalfate]

!! How do you create such big updates !! Everyone who does this leaves me in awe.. Someday I hope to be that good.