3D resolution setting extended down to 1/16

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/main.rs

@@ -73,7 +73,7 @@ fn apply_settings(s: &Settings, r3d: &mut R3d) {
     r3d.outlines = s.outlines;
     r3d.set_wall_detail(s.wall_subdivisions());
     r3d.max_lights = s.max_lights as usize;
-    r3d.render_div = s.render_scale.clamp(1, 4) as u32;
+    r3d.render_div = s.render_scale.clamp(1, 16) as u32;
     audio::set_volumes(s.music_volume, s.volume, s.muted);
 }