Viewport: hidden edges no longer show through faces, and thin or coplanar faces stop z-fighting (#1434, #1739) (#1768)

Thanks @CamWight.

apps/solidcraft-web/src/main.rs

@@ -27,7 +27,9 @@ mod web {
 
     const CANVAS_ID: &str = "solidcraft_canvas";
     const LOADING_ID: &str = "solidcraft_loading";
-    const DEPTH_BITS: u8 = 24;
+    /// A 32-bit float depth buffer (no stencil): WebGPU and WebGL2 both have it, and the viewport
+    /// draws it with reversed depth, whose precision follows the distance from the eye (#1434).
+    const DEPTH_BITS: u8 = 32;
 
     /// Seconds between autosaves of unsaved work.
     const AUTOSAVE_S: f64 = 30.0;