Hippo Tycoon on iOS (second iOS app): hippo_sim as an xcframework, SwiftUI + RealityKit #2883

Part of #2875. After Park Hide & Seek's iOS build is through review.

• hippo_sim (rules + oil sim, already held to the TS twin by a state hash) is the first Rust core shipped through the iOS lane's xcframework script, so solo play against bots can run on the phone.
• RealityKit draws the hippos, geyser and jungle from the same state; the look follows the three.js scene.
• Online rooms go through the edge, as Park Hide & Seek does.
• Same App Review list as the iOS lane, plus Game Center if achievements land on Steam first.