refactor(ui): extract adaptive panel rail layout

src/ui/panelRailGeometry.js

@@ -0,0 +1,55 @@
+/**
+ * Resolve a vertically centered panel slot inside a HUD rail while respecting
+ * live rectangles that intersect that rail above or below the viewport center.
+ */
+export function resolveHudRailLayout({
+  viewportHeight,
+  panelHeight,
+  laneLeft,
+  laneRight,
+  obstacles = [],
+  baseTop,
+  baseBottom,
+  gap = 12,
+  align = 'center',
+}) {
+  if (![viewportHeight, panelHeight, laneLeft, laneRight, baseTop, baseBottom]
+    .every(Number.isFinite) || viewportHeight <= 0 || laneRight <= laneLeft) return null;
+  const midpoint = viewportHeight * 0.5;
+  let safeTop = Math.max(0, baseTop);
+  let safeBottom = Math.min(viewportHeight, baseBottom);
+
+  for (const rect of obstacles) {
+    if (![rect?.left, rect?.right, rect?.top, rect?.bottom].every(Number.isFinite)) continue;
+    if (rect.right <= laneLeft || rect.left >= laneRight || rect.bottom <= rect.top) continue;
+    if (rect.bottom <= midpoint) safeTop = Math.max(safeTop, rect.bottom + gap);
+    else if (rect.top >= midpoint) safeBottom = Math.min(safeBottom, rect.top - gap);
+  }
+
+  safeBottom = Math.max(safeTop, safeBottom);
+  const availableHeight = Math.max(0, safeBottom - safeTop);
+  const renderedHeight = Math.min(Math.max(0, panelHeight), availableHeight);
+  return {
+    top: align === 'start'
+      ? safeTop
+      : safeTop + Math.max(0, (availableHeight - renderedHeight) * 0.5),
+    maxHeight: availableHeight,
+    safeTop,
+    safeBottom,
+    constrained: panelHeight > availableHeight,
+  };
+}
+
+/**
+ * Tactical HUD gives an expanded right-rail panel the whole control lane.
+ * Other HUD layouts keep collapsed launchers visible for quick switching.
+ *
+ * @param {object} input Current rail state.
+ * @param {string} input.hudVariant Active HUD layout variant.
+ * @param {boolean} input.hasExpandedPanel Whether any rail panel is expanded.
+ * @returns {boolean} Whether collapsed sibling launchers should be hidden.
+ */
+export function shouldHideCollapsedRightPanels({ hudVariant, hasExpandedPanel }) {
+  return hudVariant === 'tactical' && Boolean(hasExpandedPanel);
+}
+