feat(scene): draw nonprint light, camera and geo-location glyphs

Lights, camera views and the geographic-location marker had no on-screen
representation. Add display glyphs for all three:

- Lights render through a new EntityType::Light: a cone/flashlight for spot
  lights, a wire sphere for point lights, a sun for distant lights, sized in
  screen space (fixed-world fallback).
- Camera views (perspective VIEW records) and the GEODATA "daisy" marker are
  synthesized into the model-space resident wire set from the document, since
  they are not entities.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/scene/camera_ops.rs

@@ -86,6 +86,8 @@ impl Scene {
             front_clip: 0.0,
             back_clip: 0.0,
             twist_angle: 0.0,
+            // OCS saves an orthographic model view, not a perspective camera.
+            perspective: false,
         }
     }