3D: WebGL renderer created without stencil buffer since Three.js 0.185.1 upgrade #9252

Description

Since #8853 (commit 7dd4d13, "Upgrade to Three.js 0.185.1"), the THREE.WebGLRenderer created in GDJS/Runtime/pixi-renderers/runtimegame-pixi-renderer.ts no longer has a stencil buffer.

GDevelop does not pass stencil to the renderer, so it uses the Three.js default, which changed from true (r160) to false (r163+). Extensions relying on the stencil (cross-section capping, portals, masks...) silently break: the stencil test is ignored.

Request: pass stencil: true when creating the WebGLRenderer to restore the previous behavior.

In game

A "see-through" extension cuts the walls in front of the hero and caps the cut with lids drawn only where the stencil is non-zero.

• Before (Three.js 0.160.0): the cut walls are capped, the hero is visible.

• After (Three.js 0.185.1): the stencil test is skipped, the lids cover the whole view, hiding the floor and the hero.