refactor(ui): extract adaptive panel rail layout

docs/CURRENT-STATE.md

@@ -1,5 +1,20 @@
 # God's Eye View Current State
 
+## Adaptive panel rail layout
+
+`ui/layout` supplies the left/right rail layout passes, natural-height
+measurement and pure corridor/allocation helpers. The UI facade passes live DOM
+nodes, obstacle nodes, HUD presentation, preferred panels and callbacks. It
+retains observers, frame scheduling, saved/share preferences and Cockpit portals.
+
+The left rail keeps its measured collapsed heights and obstacle-safe corridor;
+the right rail follows its top baseline and preserves Display's scroll owner.
+Automatic collapse remains presentation only, prioritizes the latest explicit
+panel, and honors keyboard focus on the right. Mobile layout still releases
+desktop allocation styles. Stable Display allocation avoids unnecessary style
+writes. This extraction does not change panel positions or layout defaults.
+
+
 ## Surface keyboard lifecycle
 
 `ui/surfaces` owns the capture-phase keyboard listener, Tab cycling and return