Hill Sphere

Second test build: gravity on ships and walls reworked, plus new goggle options. Still rough; please report what you find.

• Hill Core shape: "Sphere" or "Hull". A hull core fills a box: on a Sable ship the whole ship (turned with it), so a ship of any shape has a floor; on the ground a cube. New cores start at level 4 (1 g)
• "Down" turns toward a floor under the feet: step off the edge of a small planet and you land on its side, walk up to a wall the field leans toward and you stand on it; a hop no longer turns you, and the turn no longer flickers on stepped surfaces
• Air control (WASD along the look, space and shift along "up") only in free flight; normal jumps are vanilla
• Fixes on ships: no more falling through a planet when "down" turns, no sliding on the side of a ship, no runaway speed, the camera and the light on the model are right on walls, the crosshair aims from the head
• Overlapping fields blend as vectors: two pulls cancel smoothly on the line between cores, an attracting core next to a repelling one no longer throws the body sideways, three cores do not jump
• Goggles: faces you can stand on are marked on Sable ships too; the seam between two fields is drawn where the fields really split; client settings for the Boundaries layer (hillsphere-shell.toml: presets, colours, density, spin, pulse, wave, flicker, fade-in)
• Rain and snow lean along the field (client option rainEnabled in hillsphere-particles.toml, rain sets how far); particles fall along the field too (enabled, strength, range)
• Own creative tab; the core settings screen is no longer blurred; the goggle overlay is drawn after clouds
• Camera follows the turn along an arc, ship levitation scales with the field radius