refactor(ui): extract adaptive panel rail layout

docs/CODE-BOUNDARIES.md

@@ -213,3 +213,21 @@ current visible/enabled controls for each key; ordinary movement within those
 boundaries remains native. The component honors already-handled keys and has no
 app, server, storage or network dependencies. Its package boundary is checked
 independently from the standalone screens that consume it.
+
+## Panel rail layout
+
+`gods-eye-view/ui/layout` exports synchronous `layoutLeftPanelRail` and
+`layoutRightPanelRail` passes, `measurePanelNaturalHeight`, and the existing pure
+corridor/allocation helpers. Separate modules own left placement, right placement,
+DOM height measurement and rail geometry. They import no application, renderer,
+server, storage or network modules; package checks build this entry independently.
+
+Callers supply rail/obstacle DOM nodes, the viewport, HUD state, the preferred
+panel, disclosure/retry callbacks and the left measurement cache. Right layout
+reads the caller's Display scroll value at measurement time and restores it
+within the resulting scroll range. The left pass notifies its caller after
+alignment so the right pass can follow. Neither pass installs listeners, timers
+or observers; construction/import does no work. Scheduling, preference writes,
+share restoration and movement of controls between containers remain caller-owned.
+Existing helper imports from `cockpitMath.js` and `rightRailPolicy.js` remain
+compatible through re-exports.

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