fix(map): keep ghost pin stems terrain-relative

docs/MAP_CESIUM_REACT_ADAPTER.md

@@ -88,5 +88,10 @@ positions. The adapter only:
 - returns the current positions through `snapshotGhostPins()` for an explicit
   product save.
 
+The elevated head and stem use non-constant Cesium properties so their ground
+height is resolved again after asynchronous terrain tiles arrive. The stem
+also keeps the same material as its depth-fail fallback; an early ellipsoid
+height must not leave a visible head with its stem hidden below terrain.
+
 Motion never recreates the Cesium viewer or any provider. A renderer teardown
 stops its single animation frame loop.

docs/MAP_TEMPLATE.md

@@ -152,6 +152,10 @@ billboard до label-слоя, поэтому непрозрачная плаш
 лежащий под ней маркер вместо «рентгеновского» проступания его обводки. Text
 outline плашки отключён и не создаёт дополнительный halo. Контуры
 `surface-fill` остаются частью отдельного контракта геозон.
+Высота elevated target и его стержня остаётся callback-свойством Cesium:
+после асинхронной загрузки terrain она пересчитывается относительно уже
+доступной поверхности, а depth-fail material не даёт стержню исчезнуть при
+пересечении рельефа.
 
 ## Acceptance fixtures
 

packages/map-cesium-react/src/CesiumMapRenderer.tsx

@@ -605,33 +605,25 @@ function rebuildGhostPinEntities(
     presentation.label_hide_camera_height_meters,
   );
   for (const pin of runtime.currentGhostPins) {
-    const groundHeight = ghostPinGroundHeight(runtime, pin);
-    const headHeight = groundHeight + presentation.stem_height_meters;
     const label = presentation.label_mode === "subject_id"
       ? pin.id
       : pin.label;
     ghostPins.entities.add({
       id: pin.id,
-      position: Cesium.Cartesian3.fromDegrees(
-        pin.longitude,
-        pin.latitude,
-        headHeight,
+      position: ghostPinTopPosition(
+        runtime,
+        pin,
+        presentation.stem_height_meters,
       ),
       polyline: {
-        positions: [
-          Cesium.Cartesian3.fromDegrees(
-            pin.longitude,
-            pin.latitude,
-            groundHeight,
-          ),
-          Cesium.Cartesian3.fromDegrees(
-            pin.longitude,
-            pin.latitude,
-            headHeight,
-          ),
-        ],
+        positions: ghostPinStemPositions(
+          runtime,
+          pin,
+          presentation.stem_height_meters,
+        ),
         width: presentation.stem_width_px,
         material: fillColor,
+        depthFailMaterial: fillColor,
         distanceDisplayCondition: targetDistance,
       },
       billboard: {
@@ -731,29 +723,57 @@ function updateGhostPinPositions(
   for (const pin of runtime.currentGhostPins) {
     const entity = ghostPins.entities.getById(pin.id);
     if (!entity) continue;
-    const groundHeight = ghostPinGroundHeight(runtime, pin);
-    const headHeight =
-      groundHeight + layer.presentation.stem_height_meters;
-    entity.position = new Cesium.ConstantPositionProperty(
-      Cesium.Cartesian3.fromDegrees(pin.longitude, pin.latitude, headHeight),
+    entity.position = ghostPinTopPosition(
+      runtime,
+      pin,
+      layer.presentation.stem_height_meters,
     );
     if (entity.polyline) {
-      entity.polyline.positions = new Cesium.ConstantProperty([
-        Cesium.Cartesian3.fromDegrees(
-          pin.longitude,
-          pin.latitude,
-          groundHeight,
-        ),
-        Cesium.Cartesian3.fromDegrees(
-          pin.longitude,
-          pin.latitude,
-          headHeight,
-        ),
-      ]);
+      entity.polyline.positions = ghostPinStemPositions(
+        runtime,
+        pin,
+        layer.presentation.stem_height_meters,
+      );
     }
   }
 }
 
+function ghostPinTopPosition(
+  runtime: RendererRuntime,
+  pin: MapGhostPin,
+  stemHeightMeters: number,
+): CesiumModule.CallbackPositionProperty {
+  return new runtime.Cesium.CallbackPositionProperty(() => (
+    runtime.Cesium.Cartesian3.fromDegrees(
+      pin.longitude,
+      pin.latitude,
+      ghostPinGroundHeight(runtime, pin) + stemHeightMeters,
+    )
+  ), false);
+}
+
+function ghostPinStemPositions(
+  runtime: RendererRuntime,
+  pin: MapGhostPin,
+  stemHeightMeters: number,
+): CesiumModule.CallbackProperty {
+  return new runtime.Cesium.CallbackProperty(() => {
+    const groundHeight = ghostPinGroundHeight(runtime, pin);
+    return [
+      runtime.Cesium.Cartesian3.fromDegrees(
+        pin.longitude,
+        pin.latitude,
+        groundHeight,
+      ),
+      runtime.Cesium.Cartesian3.fromDegrees(
+        pin.longitude,
+        pin.latitude,
+        groundHeight + stemHeightMeters,
+      ),
+    ];
+  }, false);
+}
+
 function ghostPinGroundHeight(
   runtime: RendererRuntime,
   pin: MapGhostPin,

packages/map-cesium-react/test/ghostPins.test.mjs

@@ -1,4 +1,5 @@
 import assert from "node:assert/strict";
+import { readFile } from "node:fs/promises";
 import test from "node:test";
 
 import {
@@ -30,3 +31,14 @@ test("advanceGhostPins turns an escaping pin back toward its anchor", () => {
   assert.ok(geodesicDistanceMeters(anchor, advanced) < 990);
   assert.ok(advanced.heading_degrees > 260 && advanced.heading_degrees < 280);
 });
+
+test("ghost pin stems stay terrain-relative after asynchronous tile loading", async () => {
+  const source = await readFile(
+    new URL("../src/CesiumMapRenderer.tsx", import.meta.url),
+    "utf8",
+  );
+
+  assert.match(source, /new runtime\.Cesium\.CallbackPositionProperty/);
+  assert.match(source, /new runtime\.Cesium\.CallbackProperty/);
+  assert.match(source, /depthFailMaterial: fillColor/);
+});