fix: increase bounded screen draw-order depth resolution for overlapping block wipeouts

src/shaders/draw_order.wgsl

@@ -1,13 +1,12 @@
-// Positive order draws in front; zero retains geometric depth. Keep the usual
-// 0.001 NDC offset away from the clipping planes, but reduce it near either
-// plane: perspective depth can be much closer to 1 than this fixed offset.
-//
-// Using order / (1 + abs(order)) for the limited region keeps ordering monotonic
-// (including the paper background's -2). Less than half the remaining depth is
-// consumed, so valid vertices stay valid. Out-of-range/behind-eye vertices get
-// no offset and remain subject to the real near/far clipping planes.
+// Positive draw order moves geometry towards the camera. In dense blocks,
+// child ranks occupy a narrow fraction of the INSERT depth band: a 0.001
+// NDC bias can quantize two overlapping lines/masks to the same depth value,
+// especially after changing view/zoom. Use a wider, yet bounded range for
+// CAD 2D draw order. Limit displacement to less than half the available
+// clip-space room, so we never push valid geometry across near/far planes.
+// This is a screen-only GPU change; PDF order uses its own stable sorting.
 fn apply_draw_order(clip: vec4<f32>, order: f32) -> vec4<f32> {
     let room = 0.5 * max(0.0, min(clip.z, clip.w - clip.z));
-    let scale = min(0.001 * max(clip.w, 0.0), room / (1.0 + abs(order)));
+    let scale = min(0.02 * max(clip.w, 0.0), room / (1.0 + abs(order)));
     return vec4<f32>(clip.xy, clip.z - order * scale, clip.w);
 }