Document radial pads, draped trail reveals and input options

Describe the radial disc envelope, corridor backing and reveal control,
rectangular input pick windows and optional horizon ellipsoid. Record the
launch-pad and Transit restoration and the Street Level and CCTV callers.
Explain synchronous Transit and reveal construction and surface readiness
for classified ground materials after camera changes.
Cesium remains the appearance and interaction reference; this documentation
changes no behaviour. All eleven coupling counts remain unchanged.

docs/CURRENT-STATE.md

@@ -218,6 +218,15 @@ one application, and only the globe-bound parts move to the next engine.
     engines, and `scripts/qa-ground-looks.mjs` drew the jam line and the
     route on Cesium as the old materials did, with no pixel changed at four
     moments of the pulse and the dashes.
+- **Ground and input parity.** Space Missions draws its 500 m launch-pad
+  zone with the radial ground material: faint fill, bright soft rim and
+  emission, classified on terrain and tiles. Transit draws its age-banded
+  trail and dark backing as ground corridors. The active segment uses a
+  shader reveal, retaining its geometry between segment crossings. Navara
+  composes both in the ground pass after tone mapping. Street Level's 9 px
+  pick window and CCTV's custom window and drill limit go through input
+  subscriptions. Street Level's lowered horizon ellipsoid is a projector
+  option on every engine; default callers retain the WGS84 horizon.
 - **Shared follow and Draw.** Share links read the follow target, identity and
   camera pose through the engine; their saved offset uses `camera.follow`'s
   `swingTo` option on both engines. Cesium keeps its guarded 60-degree frame