Expand voxel gameplay, lighting, full-height streaming and world imports

Add shared Rust/WASM physics, worker meshing and diagnostics, 64-chunk full-height streaming, atlas texture support, and baseline world import. Document the current implementation and include the supplied in-game lobby screenshot.

client/player-interpolation.js

@@ -0,0 +1,21 @@
+/** Separate the last server pose from the pose currently drawn on screen. */
+export function updateRemotePlayer(previous, packet, instant = false) {
+  const preserve = previous && !instant;
+  const targetYaw = packet.yaw ?? 0;
+  return {
+    ...packet,
+    position: preserve ? previous.position : [...packet.position],
+    target: [...packet.position],
+    yaw: preserve ? previous.yaw : targetYaw,
+    targetYaw,
+  };
+}
+
+export function smoothRemotePlayer(player, blend) {
+  for (let axis = 0; axis < 3; axis++)
+    player.position[axis] +=
+      (player.target[axis] - player.position[axis]) * blend;
+  // Follow the shortest arc, including when server angles cross ±π or 2π.
+  const delta = player.targetYaw - player.yaw;
+  player.yaw += Math.atan2(Math.sin(delta), Math.cos(delta)) * blend;
+}