solids-hunter: pre-release polish on the boolean-rule hunt

solids-hunter, the first-person Babylon.js game where you hunt solids defined by boolean rules, is in pre-release polish: full gamepad menu control, a working HUD speaker, spawn facing derived from the room, and rule complexity that ramps with each clear. A pre-release review surfaced five launch blockers, now fixed, gameplay screenshots landed in the README, and the shadow-pass watchdog now halves its cadence and can shed shadows entirely when quality is at risk.